I decided to take the plunge and try out MorphOS. I bought a 15" 1.5 GHz G4 Powerbook on ebay for cheap (I would have gone for a 17" 1.67GHz but the prices are obscene).
I downloaded the liveCD and will install it once the Powerbook arrives. I plan to upgrade the RAM to 2GB from the 1 it comes with and to install an SSD to replace the 80GB HDD, should I like MorphOS.