Three things, really:
1) Text boxes in Microsoft Word 2003: These things have defined my process for creating scripts, and are now so integral that I can't imagine life without them. I tried Open Office, and the boxes didn't work right. No Open Office means no Linux.
2) Photoshop's learning curve: I've figured out how to make Photoshop do what I want it to do. GIMP may do all those things, but I'd have to learn how to make it do that. I'm not interested in spending time learning how to do what I already know how to do. I'd rather spend that time learning something new that makes the comic better.
3) InDesign and my Print Broker: I have to use InDesign to make books. It's not available on Linux. Books are my livelihood. End of argument.
We can shout about technological superiority, The Cathedral and the Bazaar, market forces, and disruptive innovation until we're BSoD in the face. Ultimately everybody complaining about my choice of OS will realize with frustration that I quite amenably agree with most all of their points.
What it comes down to, really, is that I love the idea of open-source software, but I don't want to use it. Sure, sure, if everybody felt that way then open-source software would die, but everyone CAN'T feel that way. Humanity, even just the computer-using slice of it, is just too diverse. So I can choose freely without worrying that I'm somehow hurting the cause.
The open-source movement has gained enough momentum, Linux and Open Office have enough market penetration that Microsoft, Adobe, Apple, and others must compete aggressively for customers. They have to bring their 'A' game, and they have to play HARD. In that world I, the customer, win EVERY TIME. Even when I choose something too expensive and technologically inferior, I'm still choosing something that is worlds better than it would have been without the competitive marketplace.
When I worked at Novell I felt very passionate about what was on my computer. I loved certain software because my friends had helped to make it, and I was helping them sell more of it. These days I have no such connection with what I run, and that's okay. It leaves me free to run what I believe will work best for me, and I'm pretty sure my friends at Novell, Apache, UTOSC, and Penguicon will understand. Though only indirectly, their excellent work makes my life better.