Y Combinator is (we hope) visited mostly by hackers. The proportions of OSes are: Windows 66.4%, Macintosh 18.8%, Linux 11.4%, and FreeBSD 1.5%. The Mac number is a big change from what it would have been five years ago.
Linux with 11% is quite high, I like that. What seems lower then expected are the Mac numbers to me.
Thanks for sharing.