I periodically set up an AROS system.
For awhile I even kept a system dedicated to it (but have recently sold the 7600GT video card I kept for that purpose).
I am convinced that AROS will indeed "get there" on day.
MorphOS is already there, in fact its the most "there" of any of the NG OS'.
And yes, the hardware is not new.
Frank Mariak (Pega-1) has explored a port for the SAM460, but even though new, this PPC system would be slower than our current systems.
So I'll keep my G4 Macs, wait for G5 MorphOS support, and periodically check out AROS.
AROS has some serious potential (especially with ported OpenGL based programs).
If I had a powerPC kit laying around I'd definitely give MorphOS a go. Its a lot easier to explore AROS when finding an old PC for free is as simple as hopping on craigslist
Or you happen to have one left over lying around.
I bet eventually MorphOS will end up on ARM or Intel and then I'm sure I'll find the money to pony up.
Oh, and Nicholas, I'd love any documentation you could kick my way!