I posted a list of annoying bugs I encountered awhile back.
I'm having some big issues with Soulstones for one in conjunction with the still existing instance bugs.
Imp. Drain Soul seems bugged to me, getting fairly consistent latency bugs still, friend has bugs riddled on his Paladin, 2H damage bug, the 6 sec shield bug, still lotsa quest bugs, but a few are thinning out.
I'm still getting stable bugs on my Hunter, Aspect of Hawk bug, pet display bugs on both Warlock and Hunter.
Mobs spawning in objects is really annoying too.

Esp. with a Hunter's tracking
I could list more, but really, like you're going to read/care anyway.
It's really lacking balance, IMO. Warlock, Warrior and Druid really need some work, even if they did finally grow a brain in terms of Druid's bear form, I think. I've played as or constantly with all of them enough to spot some fairly large gaps. I don't really preach balance as some people sole PvE/PvP and I do a little of both, so it's my personal complaint unless you wanna talk about it more. I did make a post in the big topic.
I don't really care if I sell people copies of games, thanks. And the excuse that "well, at least it's not like WW2 Online, or Anarachy Online" doesn't sail with me, personally.
It's a good game, I've said that many times, but I really wish some of this stuff would get mentioned, adressed soon.
Sorry for not being a Blizzard Cheerleader? I dig the game, but it really could use an extra coat of paint in the form of touchups.