Hunters can viper sting while trapped, without breaking; known bug that wont be fixed. The majority of reflecting trinkets are listed as mail, making them useless for rogues or casters.
Razorgore's mind control doesnt work, thus players are forced to kill an "egg" in the middle of the room to stop adds from spawning. Ragnaros's aoe knockback doesnt work, any boss with a mind control mechanic is bugged due to that mechanic making the mind controlled player only stand still and not attack.
Countless falling through the world via fear/poly/charge/blink bugs. Numerous duping and exploiting possibilities for anyone who has played WoW emu for a long period of time.
Paladins can stack crits and essentially hit you 40 times in one swing, lifesteal and other procs are effected by spellpower yet incorrectly effected by your crit rate (rogues using lifestealing + flask of supreme power and proccing crits for 800.)
Simply going to the emerald dreams forums and looking at their bug tracker explains enough. Every pull is still exploitable in 5 mans/ubrs; stratholme barely functions, you can still alt/f4 through doors. Feenix is trash.