It will be interesting to see how GW2's PvP (organised, there is 'world' PvP which will allow for imbalances) will turn out. No leveling, equal gear, buy once no sub.
Leveling in its current state is bad, and not just in terms of PvP. It means that I can't jump in and play with my friends, because of outleveling or outgearing each other at the level cap. Progress doesn't have to be about gear stats or vertical leveling. I'm sure someone can come up with more interesting and accessible ways of progressing. There is *far* too much devotion to excluding and restricting, rather than enabling, in general.
Exploring a new 'world' is a significant factor contributing to my interest in MMORPGs. Excessive re-use of models, completely obvious zone borders, uniform mob placement and the general staticness of the world detracts from the fun.
I haven't played any non-RPG MMOs, so I can't comment on those. In general, the MMO part makes the environment feel that much more alive, even when one doesn't have one hundred friends in-game.
Ah, whatever happened to 'kill once and move on'..