My thoughts on user feedback has been to use the ResultsWindow list. By changing the text/icon, the plugin can show the number of results, an error text etc. That is the reason why there is a timer in the ResultsWindow.

A ribbon is not a bad idea, but I'm afraid that this might spam the user if all the plugins start using this approach. The ribbons are limited to only show one at the time. Without a timeout, each ribbon must be clicked on to go away, and with a timeout the user might not see the info from the ribbon before it is gone.

I believe updating the plugin text or title is the best approach to give the user input on what's going on, unless we want this kind of input in other places than the ResultsWindow?