I use OS X and Vista. My Macbook Pro has Leopard on it, it's my main machine because I have found all those perfect apps for my daily routine (Vienna for RSS, Firefox + Extentions for browsing, Journlr for writing a journal, Time Machine for backup, Adium for MSN, iCal for scheduling, Word for word processing, Unison for newsgroups, Photoshop for photochopping, Aperture 2 for managing my photos, iTunes for music, Cyberduck for FTP/SFTP, VLC for movies, and VMware Fusion for virtualization, along with some other apps)
I've also noticed I am alot more productive in OS X, especially with spotlight and quicksilver. I've had my share of problems with OS X, crashes, random things not working, etc. I am an extreme power user of my laptop, my Macbook Pro has held up and I love it.

I use Vista on my laptop and desktop for games and any other windows related tasks. I use Vista a lot too, I don't know why everyone is complaining about it, I've had a great experience with it, and surprisingly, less crashes than Leopard! I do notice a drop in FPS over XP, but I like DX10 with Crysis on my 8800GT's in SLI.

I'm on my path to becoming a Network Administrator (Getting my MCSE, CCNP, and other fun stuff) so I have to have knowledge about all operating systems. I have used linux quite a bit, never really fancied it, but I can work with it.

I also use Server 2008 and 2003 extensively, but 2008 is just so much better than Server 2003, MS did a good job on it.

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