I was actually disappointed to learn that his move was a political one. He started really great with "My strategy is to use what works best, period." That should have been the best reason to switch. It was, in my case: playing with random OSS projects is much easier on Linux because most often it's the #1 target platform for software I'm interested in.

Speaking of "use what works best": I still have the MBP to run Photoshop, precisely for that reason.