The lag is probably the most obnoxious thing about the gameplay. My main PC specs are, for reference purposes:
i7 930 OC @ 3.4 GHz
GEForce GTX 570 GPU
That's enough for maxing pretty much most other games out there. I get an immense amount of graphics lag when rendering new players or when moving to new areas (very often when moving around in the same area as well). A lot of this suggests either that the server is causing the lag, or that the game doesn't buffer new areas very well.
Other than that, though (and this has been mentioned to death in this thread), I don't actually have any noteworthy complaints about the game.