Noone knows how to write a good Chaos book anymore. And it's not just because we lack the 3.5 armoury.
The army-wide gimmick is wank! The gift of the gods table is absolute ass.
Imperial Guard: Orders.
Eldar: Run'n'shoot / Psychics
Tau: Markerlight shenanigans
Necrons: reanimation protocols
Loyalists: Chapter tactics
Dark Eldar: Pain tokens
Daemons: Warp storm
Until the eye of the god table is replaced with something good, Chaos will be in a bad place, because they're not fun and people aren't buying them.
With the above army special rules, they add a layer of tactical flexibility that gives the player more to do throughout their turn, and far more options than without them.
A chance of +1 to a random stat or some random crappy rule is asinine. It's a chore to keep track of them all, it makes people skip champions where possible and in the end, it's just boring.
Being granted unique special rules or universal ones on some of your units just for picking them is far too tempting over what chaos has.
2 Things Chaos has in common with Nids and Orks:
a good chunk of overcosted/crap units each
bad/boring/not-as-good-as-everyone-elses special rules
and anyone who reckons Waaagh is any good nowadays never had an Ork Warboss who was I8 on the charge.