Specs:
E8400 @ 4ghz
8800GTX
2gb 1066 RAM @ 850-ish
Asus Maximus Formula II mobo
XFi sound card
Game at:
54451
2560x1600x32
x16FSAA
x16AF
V-Sync off
On field in QC:
Looking forward in cockpit, fully zoomed-out: 40fps
Looking left (five Camels in view): 22fps
Looking directly up: 83fps
At 2500ft:
Forward: 52fps (x6 hun coming at me)
Left: 70fps
Up: 180fps
Dogfighting at zero altitude, lowest fps seen: 26fps
I think when I originally set 2560x1600 in config the game actually played at 1920x1200, I was getting much higher fps. After exiting the game and going back in I'm now getting those listed above. I'm guessing an exit from the game is needed after changing resolution, to 'set' it.
I can't say I notice any difference in image-quality between the two resolutions. Certainly notice the difference in size though, I actually felt a bit of motion-sickness after a while of first playing, possibly because my peripheral-vision can no longer see properly off the screen. I'm sure I'll get used to it though.