What is your best practice as a programmer to use different OS

While I think this question would need a little editing to avoid being an invite to a flamewar, I'll add some feedback:

  - I personally prefer linux (used to be Ubuntu, but now fedora or mint).
  - I used to prefer KDE and might be moving back in a few months when I get some better graphic card, although gnome 3 seems like a huge step in right direction.
  - I work together with people who love Macs, and I've been doing most of my paid work on a MBP for a couple of years. Still don't like it. Made me understand that usability is in the eye of the beholder.
  - Win 7 is great, but once you have to do a lot of the work in the terminal, it quickly becomes tiring. Also, getting a snappy setup on most prebuilt systems w/o reinstalling everything from scratch seems hard.

Linux has traditionally been the hacker's choice but OS X has gained popularity recently and Windows is so far from being a competitor.

Also, it would help telling us what you're developing cause that could change things quite drastically.

Windows; the Win32 API is great to develop applications. Microsoft puts an emphasis on maintaining software backwards compatibility.

    int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, PSTR szCmdLine, int iCmdShow) { ... }

linux,gentoo/ubuntu

OS X aka Mac for me. Run Parallels for other OS testing.

I use Arch Linux with gnome, to program in php and java. I think its brilliant, quick and stable. It took me some time to get it all working, but it was worth of it.

Use virtual machines!

It is one of the better "best practices" you can practice.

Keep whatever Windows came with your computer, install VMWare, and then spin up a new virtual machine to experiment/test in whatever other OS you want w/o mucking-up your base OS. Plus, if you hose your virtual machine, it is easy to revert it to a previous, okay, state by restoring to a snapshot.