I think Linux is a much richer development environment than OSX and much easier to manage through package managers like apt or yum. Sorry, but nothing on OSX comes close. Plus, you get an insanely rich collection of interpreters, compilers and assorted tools and it runs on just about any computer you already have.

Cygwin can make life under Windows bearable, but there is a long list of confusing things people have to deal with such as the /cygdrive tree and executables always having the .exe extension. "ls" autocompleting to "ls.exe"?