I snagged a copy of Wrath of the Lich King on my way home last Thursday, got it installed, and was promptly greeted with a 2 hour wait to get online thanks to the insane queues that have popped up after the release.
Maybe it's just a function of the server being overcrowded, but I really, really don't like playing this expansion. Mobs respawn as you're killing them, and a bunch of quests form a kind of bottleneck where the NPC will become unavailable for turnins if someone else beats you to him and starts goofy animation sequence for the next phase or where you're stuck waiting in line to kill some special mob to complete a quest.
My real gripe, however, is that the fun part of the game had been raiding, not levelling up. And now that I'm forced to do it again, I really think I'd rather not.