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.
I'm pretty sure most early Linux adopters switched from whatever proprietary platform they were using for political reasons (i.e. freedom). I'd argue that without the people who switched for political reasons, Linux would never have acquired its current level of awesomeness.
"Playing with random OSS projects is much easier on Linux"
I couldn't agree more. I am primarily a .NET/Windows programmer, but I have an Ubuntu VM that I have been using to hack on OSS-based work I've been doing recently. Package managers make it super simple to get everything up and running quickly, and mean I can keep each of my machine's VMs up to date with whatever new thing I'm mucking around with.
Speaking of "use what works best": I still have the MBP to run Photoshop, precisely for that reason.