Man, I actually read through this thread expecting to find useful information.
My system:
2500+@3000
1024mb ddr400
204mhz fsb
radeon 9800@ Almost 9800 Pro speeds
In the beta, it performs great at 1024x768 with 2xaa and 8x perf af. 800x600 gives a bit of a boost. The flashlight dips the fps just a wee bit, as does a few enemies. Id say its running about 30-40 or so depending on whats on the screen, although Ive seen it dip into the 10s, but I chalk that up to bad level design for the beta. Also, being a beta, performance in the retail game is likely to be much better. Itll easily hit 60 now in a sparser area.
Honestly people, its not going to be impossible to play. Theres something about the fact that the game is really dark and moody that makes a more average frame rate (30 or so) very bearable. Almost seems more cinematic in a way. AA is almost unnecessary its so dark.
That being said, you will probably have to play at a resolution lower than youre used to, but again, its so dark, you honestly dont notice it nearly as much. I wouldnt touch the game with a gf2, or even a gf3 for that matter. I played it a bit two years ago with a gf4, and it was pretty slow, but that was also quite some time ago.
Personally, the minimum I'd want to play it with is:
2ghz, 9500/9600, 512mb ram. But these are far from minimum.
You could probably get away with, although it wont be pretty or fast:
1.5ghz, gf4 4200, 512mb ram. Certainly not for the snobs who need a fast frame rate at a high res. Youre looking at 6x4 or 8x6 here for sure, with no AA/AF.
If you have 2.5ghz, 9700 pro, 1gb ram, or more, and youre golden, and have NOTHING TO WORRY ABOUT.
Having a gig of ram helps immensely with load times and getting rid of hitches in game.