Suggested by Bryan Clark; we should display a list of things that changed (i.e. what is requiring the restart) when clicking on the "restart required" tray icon.
Glad someone else reported this was about to make the same request. My main motivation was this. In some cases a restart is not critical for what I need to do quickly, can I delay the restart? Without knowing what is requesting the restart I'm mostl yjust doing a restart if I'm not in a rush.
The update manager shows an icon besides the packages that require the restart (or logout), so I guess this could be considered fixed now.