Whatever SE did, they got it right.
According to the minimum specs, I shouldn't even be able to run the game, but since the last update I am running full screen at 1920 x 1200, graphics low but not at minimum, very little mouse lag, and I would guess around 27 or so FPS. The menus and maps take a second or two to pop up but combat and everything else is smooth. No chop from bad framerates either. I still think a lot of the menu delay is from server lag though.
Prior to the patch I was running in windowed mode at 1280 x 720, and it's running better now, with full screen and the higher resolution, than it was then.
While I haven't tested any busy parts of the city yet, the game is playable. Although I probably wouldn't join a group or anything.
Athlon 64 X2 4200 (2.2Ghz)
3Gig of memory
Win 7 Pro x64
The fan on the GPU picked up a little after about 10 minutes, but speedfan was reading the GPU at about 71C and the cores at about 42C, which isn't that far off of normal.