I play all the versions of Chaos so I'll chime in a bit on them:
Warriors are the kind of army that can just about fit most peoples' play style ... aside from people who want to sit back and shoot all game. You want to do horde? Get a ton of marauders and hounds. You want a small elite army? Warriors, chariots, knights, & skullcrushers will fill the roll nicely. You want somewhere in the middle, mix and match. You don't have to do the monster mash army. I don't and I do OK in games. You can go w/ a lot of magic as well or you can go w/ just a little. I play a lot of small games and I do OK, again, just bringing a lvl 2 vs others who can, and do, bring lvl 3 & 4 casters.
Daemons are a little different due to the wacky Reign of Chaos table. It can do nothing (which is most of the time) ... or completely ruin the game for one of the players. They are not the power-gamer army they used to be (thank the dark gods!) but they are still good. Nurgle has pretty much taken the top spot as opposed to Khorne being the goto deity in the last book. There are still 'auto-takes' like the "Skill Kannon" ... well, ok, that's about the only one ...
I play a mostly Slaanesh army w/ the support units changing on a regular basis depending on what I feel like throwing in. The army composition generally falls in the moderate range for model count. Be aware, though, that you will be needing to play a larger game to get a high lvl caster. Greater daemons and daemon princes upgraded to lvl 4 are PRICY! Not that you can't do a lot of magic. For that you can spam horror units and heralds of Tzeentch.
This one's a bit harder as it's probably going to be the last book to get redone so who knows what GW will change this time (this army changes so much every time they redo the book). The large monsters are pretty much crap for their points. There's been some success w/ minotaur blocks but most armies are 1 large block of gors, 1 large block of bestigors, throw in some chariots, solo razorgors, and harpies, great bray shaman on death or beasts, BSB w/ 1+ AS and The Beast Banner, and 2 or 3 lvl 1 shamans w/ shadow or beasts dancing around The Shart of the Herdstone.
Other non-elf armies:
I do play VC but it's more fluffy aiming at the old Lamiah (sp?) army using mostly skeletons, grave guard, and black knights, and aiming for all female characters. Throw in some spirit hosts, wolves and other random stuff (a varghulf just because I painted it) and I'm set there. It does work ... -ish ... but it requires a bit more tactics (maybe why I lose a lot
). Many players go the route of no zombies so that's not an issue. They're just useful as you can always take them beyond starting size and they get an extra die for Invocations.
I've seen Skaven played successfully w/o the slave hordes. I've played against double clanrat buses w/ either stormvermin or plague monks, 1 a-bom, 1 warp lightning cannon, some rat darts, and other random stuff.
--Dwarfs are all about infantry and are a low to average model count army. Lots of artillery and the troops are hard as nails.
--Bretts (which are due out next if the rumors are correct) are all about cavalry but who knows what changes will be in the new book. Again, a low to average model count army.
--O&G are just a weird army to play. They can bust people up or fail in spectacular fashion. They're a moderate model count (orc heavy) to horde (goblin heavy) army. More of the "fun" kind of army. Both to play and play against.
--Ogres - the ultimate in low to moderate model count army. One of the top armies out there w/ their cannons that can move and shoot and killer monstrous cav. Their deathstar units are pretty deadly though spamming I-based nuke spells could be deadly against them.
--TK are a bit like VC but a bit harder to play. Not had any real experience vs the new book. I hear pretty much everything is hit-or-miss.
--Lizards - I have no experience there.
I have played against WE and DE quite a bit. Both very shooting & magic heavy armies when I play them. Haven't played against the elite infantry DE army style yet as my usual DE opponent has been MIA in the Warhammer world for some time. WE may change a bit now that the new book has dropped.