Read a Book – IA 13 Gamechangers

I've been through IA13 a few times now.  There's a lot of repetition from the past, of course.  Nothing new in the way of Daemon engines, a new tank, new(?) land raider pattern.  The biggie is the Lost and the Damned AssMill faction, though for competitive play, it ain't that big.  You can find a comprehensive review of the units on many longblogging sites you already know about.  Today, I'm just going to talk about the game-changers.  These are the units that might make it into your army list if you're bringing the cheese.

Unsurprisingly, these are all infernal relics, meaning you'll need to bring Abaddon(nope), a Warpsmith(Prob not), or a Sorcerer with Malefic(yup).

Chaos Relic Sicaran Battle Tank -

AKA the Wave Serpent Killer, To Improve a Predator, The Many-Dollared Purchase
BS 4, 13/12/12, 3 HP, Tank, Fast

Not a lot of options on this one, and you don't need them.  The primary weapon is the TL Accelerator Autocannon, 48" S7 AP4 Rending Ignores Jink.  Free heavy bolter!  Free extra armor! 135 points base.  You'll probably add a dozer blade to ensure the fastness lets you pull a late-game objective grab.  I'd recommend daemonic possession if you're allied with daemons for cursed earth synergy.
The armor makes it super survivable, and because it's fast, you can put it on your backline to avoid that pesky melta-drop.  You won't be doing a lot of damage to knights, or AV14, but at least rending gives you a chance.

Chaos Spartan Assault Tank
AKA The Big Box, Daemonette Containment Area, The One That Pretty Much Looks Like A Stock Land Raider

BS 4, 14/14/14, 5 HP

If you ever wanted a Land Raider to be useful, this is the one.  Now that we have proper battle-brothers, we can stuff daemonettes inside this thing, doing the work that Berserkers of that One God always wanted too.  You get quad lascannon sponsons which, unlike regular lascannons, are likely to kill a rhino in one might salvo.  You get 5HP to actually survive the terrible damage your opponent will do to it.  This is the premiere chassis to stick a Legacy of Ruin on, because if you're using one, your strategy should hinge on it.

Chaos Fire Raptor Gunship

AKA Close to How It Sounds in the Books, The Bank-Breaker, The Often-Proxied
BS 4, 12/12/12, 4 HP

Damn this thing is sexy.  Comes with two turret mounted quad heavy bolters which you will switch out for reaper autocannon batteries for your maximum number of fingers.  These bastards both fire independently and don't count towards total weapons fired.  The avenger bolt cannon fires seven times like a baleflamer, TL.  You get Large Blast S5 AP6 missiles which ignore cover, four of em, for fifteen points, replacing the useless ordnance missiles de plane comes with.  So you're firing on three targets a turn, burning armor or forcing jinks on two vehicles, and eradicating guardsmen and orcs.  What more could you ask for?

Chaos Kharybdis Assault Claw

AKA The Nightmare of Assemblage, The Table-Filler, The Daemonette Containment Area MKII
BS 4, 12/12/12, 5 HP

Coming with inertial guidance which you need because this thing is HUGE, it seems really expensive.  Well, it is, but it can do a lot, which is more than most things that are expensive can do, which is nothing.  Comes stock with daemonic possession so it rocks a 5++.  It's bringing 20 models in it, and with frag assault launchers, they're going to do some face damage.  You can flat out 12" after the drop, so it can be placed somewhere safe and moved aggressively, or placed aggressively and moved somewhere safe.
It's an assault vehicle, and your precious tainted children can hide inside of it till turn two, when they can assault.  Out of any side of this giant thing, after it moves 6".  If you're used to buying 40 daemonettes and getting 20 into a possible turn two assault, you'll appreciate paying a bit extra and guaranteeing that turn two assault and only buying 20.
Also comes with five storm launchers, which are S6/AP5/Heavy 2/TL/Pinning.  They can all fire independently.  So you have a good chance of pinning some of that gunline your ladies are going to claw or punch or whatever they do exactly.

Chaos Rapier Weapons Carrier (not a relic)

Ok, you're going to have to pay 55 points a unit (artillery piece and two marines) because nobody wants Quad Heavy Bolters.  But for that, you're getting 4 T7 wounds with a 3+, and a twin linked S9 AP 1 ordnance shot, which means that it almost always hits, and almost always pens.  You're taking three, because you don't like giving up KP.  Finally, some decent anti-tank for chaos.  Of course, they're going to flee after a knight lights them up and kills half of them and they check their LD 8.  And you wanted them to kill that Knight.  Nevermind.  Off the list.

Sky Assault

Wall of Martyrs Defense Line w/ Comms Relay - 65
16x Plague Bearers -145

Chaos Sorcerer w/ Psychic Pet - 75
19x Cultists - 86

18x Cultists - 82

Kharybdis Assault Claw - 265
20x Daemonettes - 190
Herald of Slaanesh, GR(Etherblade) - 55

Kharybdis Assault Claw - 265
20x Daemonettes - 190

Dreadclaw Drop Pod - 100

Fire Raptor Gunship, Reaper Batteries, Balefire Missiles - 225
Fire Raptor Gunship, Reaper Batteries, Balefire Missiles - 225

The Plague Bearers hold the Martyr Line.  Most armies can't shoot that off.  The dreadclaw is really just hanging out and trying to grab a far-off objective.  It's there to make it 3/2 drop pods so both KACs can come in first turn.  Second turn, both KACs open up and dump daemonettes out, and hopefully both FRGs show up to unleash hell.
Most lists will really struggle with 40 daemonettes striking at initiative 5 turn two.  Most struggle with 20 at I1.  This will gut the hell out of a gunline.  Against tau interceptors, you can probably find some cover to drop behind and hope they don't kill the KACs.  Against Knights, well, you're screwed, but I still don't know how Chaos in any form hurts them.  Keep your cultists in reserve for as long as possible with the coms relay.  When your sorcerer comes in, cast some summoning! It's what he's there for.

Renegades (Lost and the Damned)

Ok, I can't find a lot of gold in here.  They can do a reasonable anti-infantry job, but that's what daemons are for, and there aren't any standout anti-armor units, which is what Chaos would really like to have more of.  Everything is cheaper than the AssMill counterparts, but that irons out when you buy militia training to get them back to BS3.
I like a squadron of 3-5 Wyverns for 55 points apiece.  That could support the hell out of a flying circus.  I like the arvus lighter transport planes, 55 points for a 10/10/10 HP 3 12-man carrier.  They can carry some obSec troups that cost me 35 points.  So 100 points for a plane that will probably die and troops that probably won't.  I'm going to need a comms relay to hold them in reserve for as long as possible while the boys on the ground do the killing.  It seems very....fluffy.

Flying Circus (Ringmasters and Second-Strings) - 1849

Daemon Prince - MoN, Psyker 3, DF, WFA, GR - 295
Daemon Prince - MoN, Psyker 3, DF, WFA, GR - 295

Aegis Defense Line w/ Comms Relay - 70
20x Plaguebearers, Icon of Chaos  - 200
10x Plaguebearers - 190

8x Screamers - 200

Renegade Enforcer Cadre - 105
3x Enforcer w/ PP- 35 each

Arvus Lighter Transport Squadron - 165
3x Arvus Lighter
Renegade Infantry Platoon - 150

3x RI Squad - 58
11x Renegades, Lasguns, Meltagun, Militia Training, Sub Flack Armor

Renegade Strike Battery - 220
4x Wyvern

Men, your job is to stay alive.  Let's hope the daemons can do the work.  We're keeping the arvus lighters out for as long as possible because they'll grab/contest objectives at the end of the game.  So it's all on our Iron Armed DPs and screamers to do the heavy lifting.  If the enemy has infantry, the Wyverns will kill them.   I'm reserving them if everyone is canned up, so they can come in after infantry are exposed.  Against a strong shooting army, especially anything that can menace my DPs, I'm going to reserve everything except the plague bearers.  Good luck killing those shrouded bastards.
The Enforcers join the Renegade Squads in the planes.  They're characters so they're stuck with them, but they commissar style keep those boys on point.  They can kill a weakened squad or vehicle with PP/MG shots, but don't count on it.
This looks like folly on paper, but I'm going to try it out.  It does have a solid backfield, far field, and midfield presence, just not a lot of killy.  I usually go for violent tabling, so a 'tactical' approach will be a little different.  The image of the battlefield blasted by violent warp energies that the pawns of chaos come in to finish corrupting is awesome.  Also the always-implied cowardice of the renegades radioing the comms with excuses as to why they're not ready to come in yet.