Yeah, I'm in the same (weird) boat. I've been using Linux as my primary OS for so many years (about 10, now) that a Windows or Mac machine feels hopelessly short of applications to me. I know the reality is the opposite...it's just that when I think, "I need to draw a new icon", I don't think "open Illustrator", I think "open Inkscape", and almost every "I need to..." thought involves the command line (because I work faster there, mostly), and Mac OS X and Windows are hopelessly baroque when it comes to the command line.
Then again, these days, I use so few "Linux only" applications that it would probably be easier than ever to switch. My "regular usage" list is: vim, Firefox, Thunderbird, Perl, bash (and all of the GNU tools, like sed, grep, find, locate, awk, etc.), GIMP, Inkscape, VNC, KVM. But I'd still have to have Linux boxes or virtual machines around, because I need build environments for a dozen or so Linux distributions. And bash and the GNU tools are so vital to my workflow that I'd be suffering a lot of the time.
So, I've considered getting a Mac so that I'd be surrounded by great design (I'm becoming more of a designer and usability guy within my company every day, and my design sense is still woefully inadequate for the job, and I've read on numerous occasions and from numerous sources that one great technique for improving is to surround yourself with great design), but it'd certainly be painful.
Also, middle-mouse-button paste is vital to my happiness, and neither Mac OSX nor Windows has it.