Well, I play Serious Sam HD on deathmatch servers sometimes (when not sp'ing).
Before, I had a computer that barely met the minimum requirements, so to say.
With the settings that allowed me to see well enough[1] I used to have 15-35 FPS on deathmach servers. (30-55 FPS on SP.)
Now that I bought this new computer, I have 70-120 FPS on deathmach (90-120 is SP). And I must say, with this increase in framerate, I suddenly started to get ~2x frags to what I used to get on my old computer! Double the frags? Suddenly, after getting a new computer? Quite obvious, the extra FPS helped me a lot. Also, I started to do much better on SP too. No wonder - this game is VERY fast-paced. Faster paced than any other game I played.
[1] The graphics of this game have insanely huge customization options. And by saying "so I could see well enough", well, I'll give You an insane example of customization: On this game, I can easily set the graphics to run at few 100s FPS... but make it unplayable due to one of the options making the game, uhm, render the graphics in a rendering resolution of [!!!] 16x16 presenting it in 1080p =d