I have always thought that would be AmigaOS4, but the simple fact is, even if it were available (and hardware weren't an issue), I'd have little if any interest in paying that extra money for a slower PPC solution versus the x86 dual core.
This is just simple reality, unfortunately. The price / performance gap used to be a big problem. Now it is an unsurmountable problem. Nowadays the best effort by ANY PPC system has to be considered retro, including Pegasos II.
