Thousand Sons are so much more durable*
*Against damage 1 at least. Both Rubrics and Scarab Occult get +1 to their save against damage 1 weapons, basically giving them a 2+ save against lasguns, and allowing the units to effectively ignore the first point of rend.
Relics are gone
As far as I could see, at least. All the entries have access to a range of standard options, but I couldn't see any of the classic (or even new) daemon weapons, relics, and trinkets. I suppose it makes things a lot simpler (and cheaper) but it does meant my burning brand Warpsmith is now redundant.
The psychic phase is much more streamlined
A lot of the randomness has been removed from the psychic phase. Chaos has gone from at least a few dozen psychic powers to about 4 (and maybe a couple of god specific ones for daemons). Whilst it does limit the options available, the new powers are pretty good, including a free extra movement and mortal wound-inflicting spells.
Magnus is a beast (still)
He goes up from 7 to 18 wounds, is strength 16 (as there's no caps on these values anymore) gets +2 to casting and denying powers, and can fly pretty fast. He's still expensive, but he should still be able to go toe-to-toe with any unit, HE can still turn stuff into spawn too (but only models with the CHARACTER keyword now...)
We're going to get MANY more Forge World toys
As well as the main Chaos index, I've pre-ordered the Forge World equivalent. At only £15 (not a typo, genuinely £15!), Chaos will have access to even more heresy tech, including Deredeo and Leviathan Dreadnoughts, Sicaran Venators, Scorpius Whirlwinds and the titanic Mastodon. I definitely have to make one of these now! I do have a spare Land Raider and a few Russ/Rhino hulls I could salvage...
I for one am looking forward to this next edition, and over the coming weeks, I'll be sharing with you all my plans for the army, including variant formations and forces, from Sekmet Conclaves to Tzeentch robot battlegroups to rival the meanest Nidzilla forces.