I upgraded my PowerBook to the latest Tiger release. In 20 years of working with computers I never experienced a system upgrade that was so easy.
After cloning the complete internal harddisk to an equally sized external one (with Carbon Copy Cloner) I did a clean re-install of MacOS X 10.4 Tiger. Tiger comes with a migration wizard that copies all data and settings (and it seems “all” really means absolutely everything – including bookmarks in any browsers, photo libs, music, desktop settings, aso). I opted against copying applications – I wanted to re-install just those I really needed. After the new mail application re-imported 90.000 e-mails I was set to go: I just had to copy over the applications I wanted to keep from the cloned partitions. No “re-install” necessary (installing and un-installing applications by simply moving its icon around is something I first saw in NeXTSTEP in 1994 by the way – something windows is unable to do up until today!). I never had to answer any mysterious system-related question or re-configure anything I had configured in the previous system. I hardly can imagine a simpler way to upgrade a system.
And in addition to that: The new system feels more powerful and snappy. The spotlight search engine allows me to manage the 90.000 E-Mails as if they were 900. I can find data that I didn’t knew I still had on my harddrive in a second. And again this system upgrade improved the performance of the user interface like the others did before.