When viewing TV shows under "Shows", hovering over a series should display the "Tag" option, just like for movies. Right mouse context menu should also display "tag" option, just like for movies.
How about some more transparency and editability (could be opt-in in the preferences) on what is sent to the tvdb.com during lookup? This could be useful when some fine tuning of fields may be needed to isolate the exact episode.
When setting a TV show's "series" tag (this would probably apply to other tags also), leading and trailing spaces should be trimmed. I had "Archer" and "Archer " showing up as separate shows.
When dragging an episode or series or movie from MC and dropping it in a file location (explorer, desktop etc.), MC needs to "release" straight away, otherwise it locks up for the entire duration of the copy.
When pressing refresh in the "Shows" or "Movies" library views, the cover art should also be refreshed (currently does not refresh if you just updated cover art for a movie or show). Perhaps the cover art should just update automatically without having to press refresh or switching to another library view and back again.
When updating multiple episodes using "Get Movie & TV Info", new values don't display in list view straight away, you need to hover the mouse over them for it to update.