I have a Digital Audio G4 with a Sonnet Crescendo CPU upgrade (1.7GHz), 1.5GB RAM, and an ATI Radeon 9000 Mac Edition video card.
I couldn't get 9.2 to work for the longest time on this thing - 9.1 ran fine, but as soon as I upgraded to 9.2, the machine would lock up right before loading the desktop.
Removing the Multiprocessor folder from the System folder fixed this. However, I can't put the machine to sleep. The error I get is:
Your computer can't sleep because some system software is missing. Reinstall the software that came with your computer.
It's not a huge deal, and if the tradeoff for getting 9.2 to work is that I'll lose sleep capability, I'll live. I'd like to get it working if I can, though.
Secondly, the internal speaker doesn't work in OS 9.2. It was working in 9.1, and it works before 9.2 boots (e.g. there's a boot chime). I hooked up a USB speaker in the meantime, and it works fine.