> The iMac seems to handle the CPU scaling better [...]
> where as the PM pegs it at max frequency always

Yes, according to the MorphOS team, MorphOS runs the iMac's CPU at half the nominal clock rate (i.e. 1.05 GHz for the 20″ model) whenever CPU load is below a certain threshold. Would be nice to have this feature implemented in MorphOS for PowerMacs as well one day.