using lesser than native resolution is fine for me. friend of mine also has it in a window though. GTX280 here with latest official drivers. desktop composition (aero) off.

flying around ive not needed to look at FPS figures at all really. i have been able to set some higher settings too. even at 20-25 fps its very very smooth. i believe that was with the trees being off issue. when i jump down in rez to 1600 x 900 iam nearly doubling the frames over the sea with about a 25% increase over land. however it stutters more. nothing removed from cache here.

I have noticed some graphical artifacts. like flashing tubes of thin polygons eminating from various parts of the aircraft. i had simlilar problems with ARMA2.