MorphOS for MacMini is the greatest Amiga operating system experience you can get, and it's definitely worth the registration fee. Think of it as giving something back to all those creative Amiga coders who stayed on to keep the dream alive for the rest of us.
All your old Amiga programs will run in MorphOS as if they were running natively thanks to the built-in 68k emulation, plus you'll be able to take advantage of all the modern applications people are still working hard on.