I never really got into the PvP portion of GW as much as I could have. I never really had the time to commit to finding a decent, balanced group, getting organized with them via TeamSpeak or Ventrillo, and then entering a multi-team PvP battle; for that matter, I didn't really frequent the arenas that were in the various towns. PvP was never my thing. I found the PvE in GW to be quite robust. The story was engaging enough (compared to your average MMO), but what really caught me was how important strategy and good group formation were. Unlike some other games, it's not just enough to team up with some buddies and plow through mobs of criminally-easy enemies until you get "better gear". If your team cannot coordinate or cooperate, nor seek out a balance of useful classes, you're doomed to fail.
In that sense, I really liked GW, as it struck me as a thinking man's MMO.