I was used to using windows xp in the past years but when I installed windows 7 ultimate a couple of days ago, it was so fast, smooth the computer wasn't hanging if you tried to open to many programs and when wndows explorer does not respond the rest of the computer still works while windows explorer is hanging. it is very reliable. and what I also like about it is that it downloads drivers for your keyboard, mouse and etc.
the only bad point I found so far is Bit locker. I encrypted my 500gb hard drive that had 466gb free space and when it was finished. the 500g hdd had 6.6gb free. so I decrypted it and it was back to normal.
