I use CentOS6 for my servers and I've been salvaging some Army computers that have Ubuntu on them.
Linux is great for servers... People? Not so much. Ubuntu is okay... It's nothing special though. I have not used SU on either.
As for Windows... I hear 10 is the end and you don't have to buy it. I've heard it's their last OS. May just be rumor mill as I don't much attention to those things. But I wouldn't doubt them moving more towards pads and phones. They say they'll just be doing updates for security and drivers.
I would skip 8, go to 10 give it a spin and then if you don't like it, ditch and try one of the others.