As trivial as it might seem, any upgrade is quite complex to me because I use a lot of post-stable, and even post-unstable, packages coming from my PPA. I backport packages from Ubuntu unstable, Debian unstable and experimiental, and quite often I package myself versions which are not available yet in any of the former.
Given that the PPA “copy packages” feature does not work for me (when I copy a Gutsy package to a Hardy package, it is built but never made available for Hardy from my PPA), yesterday I spent most of the day producing Hardy versions of my packages and fixing issues (what’s with the libfcgi maintainers!? why are they slightly changing the package name almost with every release!?)
In the end, the upgrade went mostly fine: everything worked save for my USB external disk, the mouse in X, and the volume control. The only missing application was KSynaptics, which I use to disable the touchpad 99% of the time (I like it better my laser mouse).
The external USB disk issue was rather easy to fix: just add usb-storage to /etc/modules.
The mouse problem has drove me crazy for a couple of hours but I finally figured it: the new xorg.conf had set the mouse to InputDevice "Mouse0" "AlwaysCore" (whatever AlwaysCore means) and the fix was as easy as commenting out the "AlwaysCore" part.
KSynaptics missing proved to be a bit more complex. The application does not work with modern versions of X.org, apparently due to X.org people forgetting about proper versioning of APIs, therefore KSynaptics’ developer decided to stop working on it and starting a new application (TouchFreeze) with a different approach. While TouchFreeze works fine, it was missing the enable/disable touchpad actions, which are the only reason I wanted to use it. But my friends, that’s the joy of open-source: I took the sourced code and a few minutes later I had implemented those actions and added a “disabled” icon like the one KSynaptics had. Here is the patch against TouchFreeze 0.2, in case you want to use it (I’ve sent it to the author to inclusion in a future release of TouchFreeze)