With the new Eldar codex out, I thought I'd give my initial thoughts and impressions on the new Eldar. This first part will look at the overall codex with later parts going over individual units and formations.
Introduction:
Overall, aside from the Destroyer weapons galore (all Distort weapons are now Destroyer weapons), I think the codex is very balanced. I like how many units that I previously thought were bad or unusable might turn out to be pretty viable in competitive play. Specifically, I am especially excited to try out the Crimson Hunter Crimson Death formation and possibly a formation of Aspect Warriors (2x Fire Dragons, 1x Dark Reapers) riding Deep Striking Falcons... But more on those in another article.

Indeed, I see that there is an opportunity to make lists with a lot of synergy and flavor which is good. For example, I suspect that to really make an Eldar army shine, you will probably need a little bit of everything-Eldar based psychic support, different units of Aspect Warriors to cover overlapping weaknesses, some Wraith units here and there as well as a sprinkling of our Grav Tanks and various support units. Wave Serpent spam appears to be dead, perhaps, but the Serpent is still a solid transport while some of our otherwise less used units (i.e., Vypers, Vaul's Wrath, War Walkers) are mandatory for certain formations so they should see some extra play.

General Overview of Special Rules and Major Changes:
Generally speaking, a lot stayed the same while many things changed or moved around. This new codex will feel very familiar to anyone that played as or against Eldar before but will also mix things up as there are many different ways to play individual units and the army as a whole.

For example, previous army special rules like Ancient Doom and Battle Focus remained unchanged as well as Weapons like the Star Cannon and Pulse Lasers also remaining untouched. On the other hand, various other special rules/units/weapons were changed like Distort/Monofilament weapons, Farseers/Warlocks and virtually every Aspect.  Overall, I can see that they actually streamlined or altered the rules for many units with some definite design elements and thought in mind. On the other hand, some units, like Wraith Lords, got the copy+paste treatment which is a shame and missed potential.

Formations:
Speaking of what's new, the new formations really shake things up. There is the overall "Craftworld Warhost" formation that has three different options for the "core" requirement-a mini formation that you must take to unlock other formations. Once you take a "core" formation, and for each "core" formation you take, can field up to 12 other formations as presented in the codex.

Some of these formations offer extra special rules for the units included while others offer no special rules but just allow you to take the listed units in the "Craftworld Warhost". For example, the Dire Avenger Shrine consists of 3 Dire Avenger units, with only one such unit having an Exarch, and they get some additional rules/benefits such as +1 BS and a once per game Blade Storm (their Shiruken Catapults become Assault 3 instead of Assault 2 for a round). On the other hand, a formation of "Outcasts" is just a single unit of Rangers for each "outcast" formation.

Also, the main benefit for the "Craftworld Warhost" is an automatic 6" for your run moves which can be pretty huge, unless you can't run, of course (i.e., Dark Reapers/Wind Riders). Overall, I think the formations are pretty balanced as they all involve some "tax" in the form of having to take some units that many don't consider very good, so you don't just get to take the best of everything without any hindrances. That is, unless you play in a format where you can take unlimited detachments in which case you can just take an Eldar CAD and ally whatever Formations you want.

Exarchs/Aspects:
One big change to Aspects/Exarchs is how Exarchs now have 2 wounds and there are no more "Exarch Powers" that you can buy for each Exarch. Instead, each Aspect has its own flavor of special rules and wargear, while the Exarch has some unique ability/Wargear specific to himself.

For example, all Fire Dragons add 1 when rolling for damage on the penetration chart while the Exarch alone gets to re-roll a failed To-Hit, To-Wound or Armor Penetration roll. This means that Fire Dragons now generally get an Explode result on a 4+ (4+3=7 which is an Explodes result) while the Exarch becomes even more reliable with his weapon, having a re-roll if he misses or a re-roll if he fails to penetrate/wound. Pretty much every Aspect has some such change with that format-overall Aspect special rules with some tweaks to what its wargear does and a unique Exarch ability.

Psychic Powers:
Some things regarding the Psychic might of the Eldar have been adjusted, while other things have stayed the same. The Runes of Fortune powers are a little different in that the "Death Mission" was replaced with a 12" bubble that grants Fearless and Adamantium Will to all affected units. Can I get an Amen to Death Mission being removed? Also, Fortune was moved to the #4 power and Eldritch Storm is now AP3 and costs 3 or 4 Warp Charges (if 4 Warp Charges it is an Appocalypse Blast!). Farseers also come stock with runes that, once per phase, allow them to either (1) re-roll a Deny the Witch attempt or (2) re-roll any dice in a failed attempt to manifest a Psychic power. All in all, Farseers are more solid Psykers with what I would consider a pretty good base discipline (Runes of Fate) as well as keeping access to Divination, Telepathy and Sanctic powers-all of which offer a lot of options for your army.

Warlocks have been changed so that they can only be taken in two ways; either as upgrades to Guardian based units (i.e., Defender, Storm, Wind Rider, Vaul's Wrath) or in what is now called a "Warlock Conclave." If taken as a unit upgrade, they are just a Mastery 1 Psyker that generate powers from Runes of Battle. If taken in a Conclave, they are a "Brotherhood of Psykers" unit and for every 3 Warlocks taken, you add 1 to the Mastery Level (max Mastery 3) and you generate a Warp Charge for each Warlock in the unit. Overall, there were no changes to the Runes of Battle powers which is ok, the powers are pretty solid.

Weapons:
As mentioned in my introduction, probably one of the biggest and most controversial changes is how all Distort weapons are now Destroyer Weapons. This makes Wraith units pretty insane in terms of their killing potential, with special mention to D-Scythe equipped Wraithguard. Now, while D-Scythe Distort weapons have a -1 on the Destroyer table (so only work on a 3+ and no "do not pass go" 6 result), they still auto wound/penetrate anything they touch doing d3 wounds! To me, the single shot weapons that could each only inflict a single hit don't seem that bad since they usually destroyed whatever they hit anyway. However, for D-Scythes to get multiple cover ignoring hits in on a unit, per weapon, and automatically pen/wound-that just makes them able to erase virtually anything if they get into position. Expect Wraith units, especially Wraith Guard with D-Scythes to be at the fore of any controversy/debate in the Eldar book.

Monofilament Weapons, on the other hand, now roll To-Wound against a target's I value but use the T value to determine Instant Death. They also no longer get +1S to I3 or lower but still are AP2 if you roll a 6 To-Wound. A characterful change that re-focuses them against low I targets and slightly less against vehicles, though S6 is still strong against AV10-11. Worth mentioning is that the Scatter Lasers lost the "Laser Lock" rule and so are just S6 Ap6 Heavy 4 Weapons while Shiruken weapons still have Blade Storm.

Overall, as mentioned above, some of the weapons got some rules moved around/changed while a lot of them stayed the same. Indeed, it actually looks like Games Workshop actually took a look at some weapons and decided to alter the ones they thought needed to be altered while leaving the ones they think are fine alone. With that said, I think they took Distort weapons a bit too far and missed opportunities with other weapons-but Games Worskhop generally doesn't understand Eldar, or the game as well as I do so whatever =). We'll just have to leave it up to tournament organizers and players to figure it out for themselves how to adjust the Distortion/Destroyer weapon rules.

Army Composition:
Unfortunately, one of the most recent trends in Games Workshop has been the removal of any option that took one unit and made it troops-such as how Draigo made Paladins troops; how Baron made Hellions Troops; and, most sad of all, how Spirit Seers made Wraith Guard troops. Indeed, one of the biggest heart breaks for me in this codex is not having Wraith Guard as troops! I can't think of an edition where Wraithguard were not able to be taken as troops in some capacity and so this just means I will have to re-adjust my approach to using them. I wish they moved Wraith Guard to troops in general but I guess I can't have it all. Wind Riders, however, are still troops which still leaves us with a very strong and mobile option for securing objectives.

Internal Balance:
Taking all of the above into consideration, there are obviously some options that are stronger than others-especially in certain contexts. This plays into the concept of "balance", or essentially how good one thing is at something compared to another option. Internally, I think the book is rather well balanced as almost everything has its use and when used in specific circumstances can really be made to shine. Some units need a bit more help to get their 15 minutes of fame on the battlefield than others but they can still shine none the less!

Indeed, you have various options for close combat/shooting regarding anti-infantry, anti-tank, anti-Monstrous Creature and anti-Flyer/Flying Monstrous Creature, depending on the target you want to engage and how you want to engage it.

For example, Striking Scorpions are better at sneaking into position with the Infiltrate/Stealth special rules and they also have Shrouding until they shoot or engage a unit in close combat which virtually ensures they have a 2+ cover save. Scorpions also have a large amount of S4 attacks plus a Mandiblaster attack which always wounds on a 4+ (6+ against Gargantuan Creatures). The Exarch can also sport a S6 Ap2 weapon that strikes at Initiative which goes a long way in tipping the combat in your favor. With that said, I can definitely see Scorpions as a hunter unit seeking out weaker/vulnerable units such as generic units with no strong CC options (i.e., Bike/Tactical squads, Necron Warriors, anything Tau).

On the other hand, if you want some more armor penetrating punch in the close combat phase against other dedicated CC units, Wraith Blades are probably a pretty good option coming in at T6 with a 3+/4++ and AP 2 weapons in one configuration. Banshees might work well if you give them some Psychic support by either casting Jinx on 2+ save units and/or Doom. Not allowing overwatch makes Banshees especially appealing against Tau-if they can get to the Tau lines.

Likewise, in terms of anti-tank/MC, you have a lot of options between Fire Dragons, Wraith Guard, Swooping Hawks and Dark Reapers-among many others. It just depends on what kind of vehicles/MCs you are planning on engaging.

External Balance:
With all of the options the new codex gives you, one must still see how those options measure up to other armies. Overall, I think that Eldar will supply you with options either superior to, or on par with what other armies can dish out in every area of the game. I also still think that the better Eldar armies will be put together with greater variety rather than simply having Serpents and Wraith Knights like how many of the lists had in the recent meta. There will still be issues of multiple Wraith Knights and ranged D weapons in the Eldar book that make Eldar appear more powerful than anything else out there but I expect those issues to be resolved between players or on a tournament format by tournament format basis. Indeed, my only complaint with this book in terms of balance is how prevalent S D weapons are and aside from that, I think Eldar are fairly balanced in comparison with what other armies can throw at you.

Conclusion:
Ultimately, without any agreement between players in terms of how an army should be constructed and without any limitations imposed by tournament organizers on what can be brought in an army, there still remains the potential for abuse by spamming certain options, such as Wraith Knights/D-Weapons. However, I suspect that those types of armies will probably be rare (hopefully) and/or with proper house rules, should be fine. For example, I strongly advocate that D weapons should do nothing on a 1, but on a 2-6 just do an auto-wound/penetrating hit with either 1 HP/Wound total or d3 as per the current 2-5 result.

Also, I think there were so many things that could have been done better with the previous codex and looking at this new one, I think Games Workshop actually did a good job with trying to either improve various rules/units or to streamline them. While the new codex still isn't exactly where *I* would have liked it to be, probably because I think I know Eldar better than Games Workshop currently does-but my hubris aside-you still have to hand it to Games Workshop for putting out what seems to be a flavorful codex with some options that I can't wait to try out.