When you play 1st person games, do you find yourself feeling a little woozy after 30 mins or so? A lot of people do. I've known a few people who refused to play 1st person games, because they always get sick. If you do it a lot, you can become more comfortable with it, but it usually never goes away.
If you had 40-60 fps, you would not experience this.
Also, a lot of games start feeling really sluggish with the mouse when you have lower than 30-40 fps. With more frames, things start feeling a lot easier to aim.
I'm the exact opposite, playing 3rd person games really causes my eyes to strain and I start getting terrible headaches.
Dead space was barable, but Lost planet 2 made me quit after 30 minutes.
45fps is where I like to game at, because it feels smooth enough for me, while it also allows me to amp up settings and keep a larger resolution.
@OP A 9800 GTX is still a great card for gaming, as it can handle it's own at decent resolutions. On the other hand, even a 460 would show a gain in performance for being 220$.