Mac:
+ Highly usable
+ Extremely sexy to look at
- Only runs on Apple hardware
- A bit pricey
Linux:
+ Very customizable
+ Also damn pretty if you use Compiz / Beryl
+ Free!!!
- Very customizable, ie confusing to noobies
Windows:
+ Large software library
- Crappy security
- Viruses up the wazoo
- People in Redmond are watching you...
That said, I've been happily using Linux for over two years now, and can't imagine going back to Winblows (oh yeah, I went there
). I've stuck with Fedora Core (now just Fedora) since version 3, although I've tried a few other distros as well (Ubuntu, Knoppix, DSL, Puppy, etc).
Still have WinXP installed though, just so I can use El Semi's CPS3 emulator to get my Street Fighter 3: Giant Attack on