According to the Wiki page for OS X, even less than you remember:

As of September 2010, Mac OS X is the second most active general-purpose client operating system in use on the World Wide Web, after Microsoft Windows, with an 8.3% usage share according to statistics compiled by W3Counter.

Then again, 8.3% of everybody using a computer on the web is a whole lot of people using Apple's flavor of Unix. And, since Apple's laptops and desktops have been selling like hotcakes, more and more people are learning how to use Unix every day...

(BTW, I just have to mention that I've never used anything but OS X or Linux on my PPC-based machines. I'm fairly sure that most Apple PPCs still out there today are running OS X.)