All I know is I just upgraded my system (more like built a new one).
E7300 C2D (2.8GHZ), 4GB DDR3, GeForce9800GTX+ 512MB DDR3, all setting maxed (16XAA, all video options set for eye-candy), and I have a dual-boot setup with WinXPPro 32bit on one hard drive, and 7 Ultimate (RC) 64bit on another. 1680X1050 @ 1024 Textures (Hi-Res PACK) and all graphics settings turned up full from within AH.
XP is streamlined, 7 is not.
I get a solid 59FPS no matter what on either OS (VSYNC ON), however with Win7 even though NET STATUS looks solid as a rock, I get a lot of lag. Moving airfields takes several seconds. Lots of rubber bullets (In a panzer shooting a Wirbel.. first hit turreted it but the next 10, most of which were at point-blank range.. did nothing then someone else killed it with one hit and I got an assist).. and everything in general just feels 'sloppy' and 'heavy'. On XP, however, everything works instantly in AH and feels light and nimble.
Now I haven't spent any time disabling services or processes in Win7 so alot of this may have to be with the auto updater or firewall or what not... but there's definitely some network goofiness going on there... And of course, it's still in BETA stage as well.