I used to have a dual-boot WinXP and Ubuntu.
Win 2000 was a complete failure (compared to 98 or XP), XP I liked probably the most among Windows. I still used it about 3 months ago, but.. the computer I had it on is a 6-year old laptop, and while the hard drive was turning into an one big bad-sector I switched to Xu. Reinstalling XP every time something went wrong would be a pain in the...
Other thing is that Xu is pretty light. With Centrino Duo,1gb of ram it works pretty well. For programming, ssh, and just having fun with terminal, Linux is waay better. The only problem is - it's impossible to find linux compatible drivers for my printer. That's probably the biggest problem with linux - many things are still incompatible.

I've been using Windows since Windows 95 and all releases since then though 7 is my favorite at the moment. I tried Windows 8 and it's not as bad as others say it is.

I did use a Linux based OS for a minute called Jolicloud but it was such a pain in the ass to get to do the basics, i was annoyed and uninstalled it. Only a serious programmer geek should stick to Linux. I'm just not there yet.

As much as I think Mac is pretty, it's far out of my price range and dual booting it is a pain in the butt. The only reason I could ever want Mac is GarageBand and that's a maybe in and of itself.

All that in mind, I wouldn't mind some alternative suggestions as long as they are easy to dual boot or I can run them in a sandbox.

The most beautiful shining star

Windows 7.
Windows 8 is just incredibly shit to use.

Windows 7 is still the best for me

Windows 7. Not bothering upgrading to Windows 8 because it seems more suited to touch screens and 7 is just fine~

Have a Mac Air and a Windows 7 laptop. Prefer Windows 7 because I'm more used to it and because I can game there. Gaming for the Mac OS is somewhat non-existant, I believe. The Mac OS is more convenient to use and more aesthetically pleasing than Windows 7 though.

Linux (Debian linux in particular).