While I'm not a hardcoe gamer, I wasn't very satisfied with my performance in Crysis 2. I got around 40-50 fps at 1280x800, but drops in the 20-30 fps in populated servers were usual, and when starting a match I got sometimes in the 10-20 fps range for a few seconds. I blamed my Core 2 Duo E8400 (running at 3.5 GHz) for that.

I purchased a Core 2 Quad Q8400 in eBay (84 €, shipping included) and overclocked it from 2.66 GHz to 3.2 GHz. Now I get around 60-80 fps at 1280x800 with drops in the 40s, lowest I see now is around 35 fps. I could do some FRAPS runs if somebody is interested.

I'm very happy with the change. I'd like to upgrade my GPU, too (I have a Radeon HD 5770), playing at 1440x900 or 1680x1050 (native) at the 60 fps would be great, but I don't have more money to burn on gaming by now (next investment: Crysis 3).