how do I detect OS X in my .vimrc file, so certain configurations will only apply to OS X?

Question

I use my .vimrc file on my laptop (OS X) and several servers (Solaris & Linux), and could hypothetically someday use it on a Windows box. I know how to detect unix gene

Answer 1

You want macunix. To quote :h feature-list:

mac     Macintosh version of Vim.
macunix Macintosh version of Vim, using Unix files (OS-X).

mac, AFAIK, only applies to old-school Macs, where \r is the line separator.