Certainly looks like we've travelled down the same road there!
This was all proof of concept really - most people on the forum will play media on their Intel Macs anyway, I myself use an old netbook with broken mouse pad hooked up to LCD, external drive & wireless keyboard, running XBMCbuntu as main media hub and it's worked great for years.
Most issues with HD playback on PPC are simply because the files are contemporary downloads - ripping your own you're in business on Powerbooks etc.