Hello all,   
This is my first post in here but im a long time lurker :D   
Just want to add a little test to the topic.     
I did a test between Win Xp 32 and Win7 (build 7048 X64).   
Sorry no Vista x64 test in this one (did not have it installed)   
Test setup:     
Intel Core I7 920 (OC@3,9GHz) 
Gigabyte EX58-UD4P bios F6 
6 Gig Corsair Dominator 1600mhz DDR3 
XFX Nvidia Geforce GTX280 1Gb OC@700 1500 1205mhz 
HDD: Samsung spinpoint F1 1TB 
Creative Xi-Fi Xtreme music 
Saitek X45 throttle 
MS sidewinder precision 2 joystick 
Tir 3 Pro 
single Samsung 22" Flatscreen   
Nvidia Drivers for WinXP: 182.08  
For Win7 i used the VistaX64 drivers 182.08 as the Win7 beta's wont allow me to use Rivatuner for overclocking, so i have not tested nvidia Win7 beta's  
they might even run better but vista drivers run just fine. 
only driver problem i have with Win7 is the black line tearing when using the mouse in the menu's en mission editor.     
screen res 1650x1080x32bit  
Settings all maxed out except water (normal)   
Nvidia control panel settings: 
AF 8x AA 8x Gamma correction:ON 
AA transparacy: OFF 
Conf texture clamp: USE HARDWARE 
Force Mipmaps: NONE 
Texture Filtering neg LOD bias: CLAMP 
Texture Filtering: HIGH Quality 
Triple buffering:ON 
Vsync:Force ON 
all other options used global default.   
Test was taken on the tarmac at Nal' Chik base with engines running and sitting in the cockpit fully zoomed out (eats more frames) 
Addon's Used: SIMMOD LoReload textures and Dragons airbase textures   
DCSmax to set affinity on all 8 threads.   
WinXP:    
Min FPS 28 (in cockpit looking back at the city of Nal Chik zoomed out) 
Max FPS 53 (in cockpit front view zoomed out)   
Smooth gameplay overall and any other then big cities a solid FPS of 60 (vsync)   
No change in FPS when using affinity check, but the sim feeled smoother when only 0 and 1 core were checked then on all 8 threads (more micro stutters when FPS drops)   
Windows 7: using only one core.   
Min FPS 21 (in cockpit looking back at the city of Nal Chik zoomed out) 
Max FPS 47 (in cockpit front view zoomed out)   
Alot of stutters when starting up and switching between in and external views even with Vsync OFF FPS drops were terrible and stayed low in cockpit 
so no smooth game play here.   
Windows 7: All 8 thread used.   
Min FPS: 32 
Max FPS: 58   
A nice boost in FPS over WinXP but not as much as i expected but this could get better when using future Win7 Nvidia and system drivers. 
Gameplay was just as smooth as with WinXP, they feel very identical but with a little FPS gain for Win7.   
   
   
For now im happy with Win7.   
If someone can get Rivatuner to work with Nvidia (beta) Win7 drivers please let me know.