I have just a minor tweak of the UI that I'd like to see. Currently the button to get rid of the progress window is labeled "Close". That term generally implies that the application is being shut down. As this is not the case here, I suggest that the button be labeled "Hide" or similar.
(That might mean that it's no longer possible to use a stock button, but I'd consider that acceptable as the current button still confuses me occasionally)
I'm not sure what it's called. It's the small one you get when you select "Update system" in the notification tray. It's not the big update application that's also available from the system menu.