First time: This was about a year or two after it came out. I was a Paladin. Got to level 56. Being Paladin pre-patch 1.11 (or 1.16? I forgot.. One of them) was a royal pain. You were pretty much useless. I remember my friend telling me to start looking for cloth gear since I'd mainly be healing in raids. I couldn't kill anything and my heals sucked. I was slow, sluggish, and boring. I quit!
Second time: I bought the game new, and started my dwarf rogue. It was fun. I quit because of timing and all that.
Third time: This time, I think I quit for good. Got that Dwarf Rogue to 80 and discovered that there's nothing to do. I couldn't PVP since my gear sucked, I couldn't do any group things since my gear sucked... It was frustrating. No thanks.
Cataclysm looks enticing, but if I ever want an MMO again, I'll head back to LOTRO.