I haven't really had an issue with the PC port. I'm not getting huge frames, but then again, I'm still on a 4 year-old rig (planning for a massive, all-encompassing upgrade sometime this year). I still have it maxed out, though, and it's perfectly playable. The 16:9 thing is a shame, though.
Mouse is a bit laggy in the menus but in the actual game, it feels perfect (unlike Dead Space 1 where it was laggy both in menus and in-game).
Playing the actual game feels great, since PCF knows how to make it feel great. They know how important responsiveness in both the movement and shooting is to the feel of an FPS, so they put clear emphasis on those things. I haven't played a game that moved or felt this smooth and responsive since, well, probably Painkiller.
Though I guess UT3 felt pretty good as well, as a rare modern example of that type of game.