Lasareth really summed up WoW very nicely. There are quests in abundance, but at later levels (40+) it is faster to just grind then to do quests to gain levels. But I'd recommend doing the quests. I power leveled my first character to 60 and I'm currently leveling my alt just by questing. It is so much more fun. But it's nice to have a 60 to fall back on in case I get ganked and corpse camped on my alt. I keep both in the same area at all times
PvP is pointless at the moment but that is changing. Of all the MMO's I have tried, WoW is the best by far.
--jaded