I am also an old computer hobbyist, with an apparent emphasis on Macs between '90 and '05. I used to try to get them up to the highest spec and newest software they could support, but found that they feel so much more usable when running either their original release OS or something in the middle. I have used Mac OS 9 and OSX 10.4 on my '99 iMac DV (PPC 750/G3, 400MHz), and they feel worlds apart to use. Same with my Performa 6116CD (PPC 601, 60MHz) on System 7 vs. OS 8.
(Of course, the rules are totally different with BSD and Linux, where you generally want the newest software that supports the architecture and it works great as long as you choose your packages wisely.)
