Suspend a distribution upgrade which is in progress

It would be nice if the Kubuntu distribution upgrade tool had a "Cancel" or "Suspend" button to stop the process. This need only be visible as long as the downloads are in progress and nothing has actually been updated. The functionality is already in place (as I noticed while upgrading to Feisty, when the upgrader failed to contact the server to get one package, and neatly cancelled and rolled back the upgrade process).

Usage cases:

A user discovers that the upgrade is taking longer than planned, and has to leave (and shut down their computer). They can cancel the upgrade and resume the next day. Or they decide that they can wait a bit so as everyone is busy upgrading to the new distribution, and they do not want to monopolise bandwidth.