Yes, I have played WoW for quite some time, so I'm not just bashing on it for fun.
I think it's a good game, but I found it rather repetitive (especially the skill system, where as a Warlock, I should only use a few skills and stay away from the other skills, lest I wanted to be kicked from a party for being a noob). I've got to hand it to Blizzard that they can make very addictive games, and there certainly is quality to be found in WoW. But not for a second have I had real fun in that game.
As Zalis said, personal preference.