I'm on a 1.5Ghz single G4 in an upgraded Sawtooth. It does have a hacked 256MB nVidia GForce 6200 graphics card and SATA card/drives so it's pretty snappy. But it's still on a 100MHz bus. So even a single 1.8Ghz G5 with the slower 600MHz bus would be a big step up for me-I'd throw down $175 in a heartbeat!
Other than the typical, mostly tongue in cheek Apple bashing, I don't know why anyone into computers wouldn't want one of these at this price. Maybe we should all chip in and buy several to send to the MorphOS developer crew ;-)