I tried OS 9.0 on two PowerMacs 8100.
The first one is a 8100/100 with Sonnet G3 266/1 and 4 MB VRAM Sonata Graphics card.
Performance is slower than with OS 8.6
CPU -5% and Graphics Mix -10 %. When the Network Assistant Startup extension is loaded the graphics become unacceptable slow -33%!!
One positive thing that I have to mention: the system is more stable than 8.6. I once had an error type 11 but I didn't need to restart.
On my second computer, a 8100/80 with Sonnet Crescendo 220/0,5 the computer often crashes at startup. Here I don't use a Nubus graphics card but the videocaddy from Sonnet connected to the original HPV-4MB-PDS Graphics card.
When the Crescendo extension (1.3.7) loads before all others I always have a crash. There are compatibility problems with other extension from Apple. When I only use a minimal set of extensions the computer boots correctly. But also here performance is slower than with OS 8.6. Graphics speed is here always -33% compared with 8.6!
I got random crashes using MacBench, Norton System Info, the Metronome Utility.
I hope that Sonnet can fix the problems quickly. And that they find a way in the future to speed up the graphics.
Greetings from Belgium