Wow, I finished WoW.
It was a good ride, it was a good game. I think Blizzard was *just* shy of creating a game I could've kept playing for years, but it's ultimately probably good that they didn't.
Basically, I ran out of new stuff to do, and the stuff I was re-doing (PvP) didn't have sufficient replay value to keep me playing. I think that's probably where the biggest opportunity lies in WoW - a more diverse and balanced PvP experience. The combat system is there, but there really aren't enough battlegrounds and the ones that do exist have some serious weaknesses.
So, cheers WoW - it was a good run.