The problem is sometimes when you are upgrading your distro, there is an upgrade failure due to overloaded mirrors.
Steve Langasek (vorlon) suggested in post #16 that in case that update-manager should offer "the opportunity later to try the upgrade again when it's more likely to succeed", i.e. when mirrors are not so saturated with requests.
I think it is too hard to import GPG-keys of repositories that you added in the "Software-sources" settings. If you add a ppa there, the key will not automatically be imported causing a failure when trying to install the program in Software Center ("can't install from untrusted source" or sth like that).
In the commandline, it works perfect: add-apt-repository ask you if you are sure to add the ppa and then imports the GPG-key. Also, apt-get asks you if you want to install from an untrusted source, if the key of a program you are about to install is missing.
Many times when we get notification that updates are available for the system we often click on install update button without even looking at the details as we know keeping the system up-to-date keeps it stable. But many times once updating is finished systems asks for reboot and everytime its not possible to reboot immediately. For example when we are working on remote sessions on telnet or ssh or editing something important on internet.
It may also be observed that untill you do not reboot the system it behaves irratically.
In the Android Market when I am presented an app update there is an uninstall button as well.
This often makes me go "oh I forgot that app was installed, I'll go ahead and uninstall it" or "I don't want that update, I'd rather uninstall that app" or "I didn't realize that application was installed and I don't need it so I'll remove it to save bandwidth and disk space."
Recently we upgraded to 12.04 from 11.10, kubuntu 32 bit. And lost google-earth in the process (OS freezes). There's a bug report on it but its not fixed yet. So to make things a bit easier why not retain a coupla previous kernels within the repositories? That way what worked prior to updates/upgrades will probably work again (if it happens to be a kernel issue like this one).
One may require some type of "Regress" checkbox within the package maintainers (synaptic, muon, whatever)... or a new source list could be implemented to make the prior kernel(s) available.
Of course would not normally regress unless a specific app critical to normal usage went bust from a subsequent kernel update (such as was my (and many others) situation).