WoW's not for everybody (nothing is, save for maybe water and oxygen), but for those it is for it is really addictive. I miss WoW, but can't play it right now. But I have this problem with all rpg-type games where I get bored of a certain class/race and think I'd have more fun with another and then switch so in all the time I've played I have one 60 and a bunch of 20-40s. I also switch servers a lot, so I have to start new toons with no money, which isn't fun.
I also like that it runs really nicely on my old iMac G4 when other mmo's (and indeed all new games), like that pirates online, run like utter crap.