Well last I ran KDE must of been 1.5 years ago, on a very crappy computer(512M, celeron). Didn't notice any lag, have ran worst though without trying KDE. I like the KDE style, Konqueror worked good for linux. IMO best UI I've used on linux, although my UI has always been windows. Kate was best text editor I've ever used, on any platform.
I use ps3 for call of duty, haven't played counterstrike in ages. Damnit I can't wait for MW3 to come out, hurry the fuck up infinity ward.