"which, BTW, makes me wonder why on earth anybody would make a Mac their development machine"
Because a development platform and deployment platform can be two different platforms.
Because a development platform and deployment platform can be two different platforms.
Of course, this only addresses Mac vs Windows - the argument becomes less compelling if you're comparing it to linux. I'm not sophisticated enough with Unix to appreciate the differences between linux and bsd, but I do like the Mac UI, and unlike windows, I get a unix prompt, which is pretty tremendous.