What Operating System do you use?

Im switching over to Ubuntu, a Linux OS, from XP Pro. Ive used XP Pro for many years now and Ubuntu is, for the most part, a very easy switch.

I hated Vista, Win7 is cool but Ubuntu uses less resources and is even easier to setup with a few exceptions.

I have a few things to work out and when I do Ill swap my main computer to Ubuntu.

So what do you use?