The CPU is an Ok speed, and once JIT gets ported over to PPC, it will be of a lot more use to emulating that old software that will not run natively on MorphOS, but as things stand, there is no JIT PPC, so if you need to emulate, your experience will be very limited...
Just to avoid confusion I like to point out that there's no 68k JIT for UAE/PPC, but of course MorphOS itself has a 68k JIT. 68k programs that work w/o custom hardware are very fast.
I think an emac is good if you can get one for nearly free to get a first impression of MorphOS or if you want to do some hardware tinkering. Best suggestion is to get a PowerMac G4 Quicksilver or MDD if you have space for a big case, otherwise a Mac mini G4 1.5 or a Powerbook 1.67 (MorphOS 3.0, probbly December this year) is the best choice.
