At least the upgrade (from 1.4.0.1 to 1.4.2 anyway) was less involved than the initial installation. Aside from the banshee source itself, I didn’t have to upgrade any other software packages.
I did learn a couple of other things in the process.
Banshee recommends not overwriting a previous installation. Specifically, it appears to look in /usr/lib/banshee-1, so either rename that directory, or uninstall the previous version. If you originally installed from source, you can go back to that and do:
make uninstall
This won’t affect any user files and settings under $HOME.
Other than that, the install of the latest release is exactly the same as the original install