I am a little bit surprised, positively. Last night at around 8 I started backing up my home directory and just two or three other directories in order to reinstall Mac OS X. The backup was quick, less than an hour for about 10GB, that's ok.
Then I inserted the Tiger disk and told it to reinstall, despite all my fear to have forgotten to backup something important. It didn't bother me with much asking. I told it to empty the disk and install a clean copy. And then I went to watch TV for a while. One hour later I came back and it was done. Cool.
But the big surprise came later. I started setting up stuff and installing the programs I needed and tuning the settings as I am used to it. But what was really cool, is that almost all applications are that civilized that the really only store their data in the ~/Library directory. So copying the old configuration data from the backup back into the new system was just all I had to do. Way cool!!! And that works for all the programs: Mail, Safari, iCal, Addressbook, Colloquy, Adium, Skype, etc.
It was less a pain than I thought ... know it only has to run smoother than before, to "vale la pena"