Minuet OS. You can fit the entire os on a floppy disk.
And OS X is not stable. If you run 1 app at a time, it is, but even windows is stable taht way. when you try to multi-task, then stuff happens.
I use an IDE, my media player, web browser, instant messenger, an office suite, and various other programs at the same time. I tried this in OS X and after that 3rd app is open, POOF! crashed. This is the reason I use GNU/Linux.
GNU/Linux is free software. Free as in freedom, meaning it respects and maintains the users' freedoms as defined by Richard Stallman. I use it becuase I hate proprietary standards. While there are fewer commercial software out there for it, there are free alternatives to every app you can imagine. Open Office or KOffice for your office suite needs, Kopete or Gaim for instant messenging. Konqueor, Firefox, Opera, or ven Lynx for web browsing, Kdevelop for your IDE, Too many media players to name (kaffeine, juk, amarok, Totem jsut to name a few) The Gimp or Krita for photo editing, Ekiga for video conferencing. There is so much software for GNU/Linux.