The Setup is a neat site. They find (somewhat) famous techie people and interview them about what hardware and software they use. I was browsing through it because I recognised some of the names, and because it's always neat to find out about tools that you don't use.
But it struck me how many people were using OS X as their primary, day to day, operating system. So I went through every one of them and added up the numbers (except Why the Lucky Stiff, because they put an underscore at the start of the domain name; stopping it from resolving).
Windows: 3.5, Linux: 3, Mac: 29.5
These folks aren't all hardcore coders to be sure, but one of the Linux users is RMS and I'm not sure he counts! It would be like asking Steve Jobs what he uses.
But gosh, that's a total OS X domination.