I have two hard drives, with OS9 on one and 10.2 on the other. I hope to get (I'd better get) a new external hard drive in a few weeks. I may install 10.4 on that, if I can afford it; I shouldn't let myself fall way behind on Apple's technology, but some of my applications (Photoshop 7, Peak, etc) may not work on 10.4, so 10.2 will still be my primary OS.
10.2 works the way my mind works, and I love it. Didn't see any advantages for me from 10.3, and I worry that 10.4 may be the same way. (what's this "dashboard" thingy?) Anybody for OS 11?
I still need OS9 for two things: Sony never wrote the software needed to import pictures from my Mavica MVC-CD1000 camera to OS10, so I go to 9 for that. Also, I still build my web pages with the very old Adobe PageMill, which was never upgraded for OS10, but which is more than I need for my simple web pages.