Running an i5 3750k at stock speeds, factory overclocked Geforce GTX 670, 16 gigs DDR3 2133 ram, and installed on SSD. Running at 1080p resolution my frame rate is around 60 or high 50's when not much is happening. When shit's going down, it drops to mid to low 40's. But in the biggest, craziest firefights I've seen it dip to the mid/high 30's. Lowest I've ever seen was 34 FPS. That was at the Crown when beta was ending, it was pretty crazy. This is all on high settings, no motion blur and low shadows.
Likely I could get a good frame rate increase if I overclocked my i5... Thinking about doing that soon.
On high (done from the in-game settings) I was keeping above 40 even 50 in the heaviest of firefights and pretty much 60 all around. This is with a HD 5970 and a stock (3.4 ghZ) i7 2600k and 16 gb 1600mhZ memory. I'm also running on an SSD.
Was really surprised. The games been well optimized from the beta. I also downloaded the new AMD Drivers that improved crossfire scaling for the game.
Now "ultra" which I tried with the .ini settings from the OP my performance really took a hit. Just under 30 with nothing happening. Anyway, I'm happy with the default high settings the game gives you so I'll stick with that.
Edit: This is with resolution at 1920x1080.
I'll save up for a 680 soon, but meh. Might just wait for the 700 series.