Well, I have installed MacOsX 10.4 Tiger on second partition. I never used MacOsX before and for me is fun to have official os as alternative boot. Now is most of MacPPC software free to download and use, so I was happy when I found MacGarden site full of old Mac Software.

Games like Fallout1, Fallout2, Warcraft 3, Starcraft, Diablo, SettlersII, AgeOfEmpire and many more I was play on my sweet little machine.
Software like TenFourFox, Office2004, Paintshop, Lightwave, Poser and many of MM, CAD, DTP, NET is also nice to have around. Even outdated.

This is on original 80Gb Hardrive, 2Gb MorphOs Sys, 50Gb MorphOsWork and rest of drive is MacOsX.
Just little press on ALT button and you can choose booting from MorphOs or MacOsX. Best of both worlds for MacMiniG4.