After installing the 21-day version of Video Converter, upgrading the Beta, the installer forced a reboot of my system. There was no apparent way to tell it to stop (to let me reboot after cleanly stopping other things). It just proceeded to reboot right in the middle of me working on other things.

This is VERY bad. You should, of course, inform the user that a reboot is required, but ALWAYS allow them to control when that reboot occurs.