I'm talking about pre-x86. I don't recall any kernel panics or segfaults when I used a G4 Power Mac back in the day; it was certainly more stable than the Windows 98 PC I was coming from.
The early x86 Macs (Core Solo, Core Duo CPU, etc) were pretty bad. I have one of the x86 Mac Minis from 2006 around somewhere.
Competitive in price it was not, and osx wasn't as good as you think it was. Kernel panics were a daily thing, and segmentation faults of quicktime while watching videos.
Reproducing file formats like wmv or divx was a quest in finding and installing the correct codec.
Also overheating, because to make it pretty they didn't add vents for the air to flow.