I occasionally use this 2+ year old version of MacUAE on a 500MHz iMac (OS 9.1). What it does, it does well so I won't bother with what it doesn't do. Anyway, I've got a plain install of 3.1 on it and everything is incredibly fast - I've certainly never seen a fastfilesystem quite this fast before.
Anyway, I'm more than positive about UAE on PPC (sounds like something a cheerleader would say...) and I'd really like to see it on non-throttled-system-bus with a 1+ GHz G4.