I have separate /boot and /home partitions. I also have a "spare" installation of Kubuntu running on an eSATA drive (where I'm typing this from). I boot the "spare", use partition editor to wipe the previous /boot partition on my main drive, copy my /home folder to the eSATA (just in case), then tell it to install using /boot and don't format /home.
So far that's worked all but one time when something happened to /home and I had to start over and wipe that out too. Fortunately I had all my /home folder stuff backed up to the eSATA drive.
