Of course, we all approach it from a personal perspective. I work at a prepress shop, and it makes submission of files to my crew alot easier if you have a Mac- and unless you only work for the Web, you'll need to communicate with prepress shops at some point as a designer. But it's not just the files themselves, it's how you navigate the OS, what apps you'll use, and all of the things we tend to take for granted. I was originally a PC user, but I still groan internally when I try to troubleshoot with someone on a PC...