I tried upgrade on 4 machines, iMac G5, iMac intel, mini G4, and mini intel. Failed on all. Went to archive and install. Worked first time on all. Other hitches...Unplug ALL firewire and USB devices except the keyboard and mouse. Make sure you are using a corded keyboard and mouse, bluetooth fails during install. Had problems with the following non apple apps.. Indigo home automation. Patch for leopard on there web site fixed server problem and also had to to a reinstall of the usb drivers from the original install package.. Parallels will fail. I downloaded the new version 3.0 and installed. fixed that. All apple apps worked, iLife, iWork, Appleworks. Time machine found external firewire drives and did a backup all by itself. Have done 7 machines now. Have three that will not upgrade due to too slow of a processor and two with memory too low. Have three more to go and one I have to wait on because it is running a database server app that has no patch for leopard yet.