I've used Macintoshes off and on since 1992. I last switched from Macintoshes to PC in about 1996. My sister desperately needed a faster Macintosh so I gave her my 9500/150 and just used my PC. I ran Windows 98, which I hated, Windows 2000, which I tolerated and finally linux, which I liked. I needed more stability and performance than I could get with MacOS 9. I'm an engineer, not a designer, so a lot of my time is spent in a terminal window or running X applications. MacOS 9 was lousy for both of these, there were solutions, but they weren't good. I could routinely outtype the terminal under heavy loads and lose characters.
Prior to Christmas I purchased a dual 1 GHz PowerMac and use it exclusively in MacOS X. It's a wonderful machine. I have my PC next to it running linux, just in case I need it. I haven't turned it on since then however.
I still have a linux box running full time, I have a MUD, it's web server and a few other things hanging off of it.