I just VERY recently decommissioned my 2nd Mac, which was a Umax Mac clone. Remember when Apple licensed 3rd parties to sell clones? I guess that was about 1998. I kept it around for a long time thinking "Maybe I'll need to run some OS8 software at some point" but that never really happened, because gradually all the OS8-only software I had came out in OSX versions.
I still have my G4 in the studio too, but it's modern enough to actually be useful for many things. Still plenty of hard drive space, firewire, USB, 1gb ram. I mean, it's not FAST by any means, but it works. I just usually can't tear myself away from the Mac Pro, more due to the 30" cinema display, than the speed of the computer itself.