I am using 64 bit windows 7, it works properly, is 99% glitch free and I am a firm believer in not fixing things that are not broken.
It also replaces applications that I like and I am used to with new ones that I won't understand or like. It will certainly not support things that I have fitted to my computer, as per their specifications page. Not a fan.
Take a read here,
http://www.microsoft.com/en-US/windo...specifications
I remember my dad getting an upgraded windows disc many years ago, after installing, he could no longer use his printer, scanner or some other things. When he asked windows why, he was told that the older hardware was no longer supported by Windows and tough, buy new ones.