Heres a link to steam's forums for some short cut commands, I did both the h and w commands along with dxlevel 81 and I just gained 30 fps average and didnt noticed anything really meaning the graphics looking shitty, they look fine.
http://forums.steampowered.com/forums/showthread.php?t=661012in case you don't understand what they are saying all you have to do is right click your shortcut on the desktop (if you dont have one there you can do it in steam as well) and then where it says "target:""C:\Program Files\Steam\Steam.exe" -applaunch 440" just add this at the end and choose whatever you want "-h 849 -w 245 -dxlevel 81"
So in the end it will look like this all together
"C:\Program Files\Steam\Steam.exe" -applaunch 440 -h 849 -w 245 -dxlevel 81"
I think you can even change -dxlevel to just 80 but i tried 81 first and it works fine for me.