The best O.S.

What in you're opinion is the best operating sistem?

Of course we all think it's the free one but I mean which of the existing O.S. is the best?.

Vista? Windows 7? One of the older XP's?

I am very pleased about my XP SP 2 professional and custom modified edition.It works smooth and it's just what I needed.

But I would like to hear what do you use and how those new O.S. work

I tryed Vista allready and I am sure it didn't rise to my expectations.

What about you?