I'm only worried about one thing: the death mechanic.
Don't get me wrong, I don't know yet if this will be a problem. But there are 2 things about it wich could annoying the living shit out of me.
1: You die and no one is around, you wait 10-20 seconds to die, and you miss the respawn timer. yay, another 15 seconds on the clock.
2: The thing I hated most about call of duty was the last stance in it. It annoyed me so much that everyone had it. It was the reason I stopped playing CoD.
Now I've got a feeling it won't be the same in guild wars2 (fps vs mmo obviously), but if it would feel sort of like it... It would annoy me a lot.