I played it for .. too long heh. My favourite class was Protection Warrior, BY FAR the most fun I've had in any game. There's just something really cool about strapping on a shield and getting the hell beat out of you and living while you friends tear them apart. :)
Holy Priest was my next favourite, healing is fun, and priest healing is amazing fun - so many tricks! I had a few DPS classes and while they were moderately fun, they got boring. Arms Warrior was my pick of the bunch - toe to toe, mano a mano, no gimmicks, you just dish out the pain. Spell casting classes were yawn inducing IMHO.
Anyway, I stopped playing a while back, I don't have the time and I played for a few years. Raiding with a good guild is real blast though, I was with a great 25-man guild for a year or so and we stomped things!
Now I'm just waiting for Diablo III for some single player dungeon crawling in my own time. :)