well, as I'm playing a healer nowadays I have to say that now starts the healing frenzies
I personally kinda hate hyjal, well its not too bad anymore as we oneshot bosses there but its nice when you get to azgalor for example. Clear 20 min trash -> boss -> oh, it actually hit that much -> wipe -> Clear 20 min trash -> boss -> oh, the fire actually hurts that much -> wipe -> Clear 20 min trash and so on

and the trash there is not walk in the park either at the start.
But on the other hand, its more rep.
addition: have to add my personal favorite, wipe on 7th or 8th wave of trash