It aint that great, its like playing another game, stats for spellcasters are fucked up for whoever had a specific gear. For exsample, priest dont get spell power from Spirit, so a full spirit priest is FUCKED lol. Talents are a mess, they combined several talents into one and now you get 1 talent every 2 levels. You cant start with 3 different specs. Example: you cant have 1 point in holy, 1 point in disipline and 1 point in shadow, you have to UNLOCK 1 at level 10, then the other specs are locked untill you have 31 talents spent on that one you UNLOCKED. And when you unlock a second one, the third one remains locked.
Personally, I dont like Cataclysm, they should of left it like it was.