Ideally, IMO, if you save your TV recordings to a folder and that folder is "watched" by MC so the Shows are automatically imported, it would be desirable to have "Get Movies and TV Info" process run automatically and update/overwrite all fields. I think this method would work well in those cases where the TV Show's epg data includes "Series Name, Season Number, and Episode Number".
If someone did not want the automatic update/overwrite, they would not have MC "watch" and "import" from their (temp) recorded shows folder. In this case, they would just manually move their recordings from their temp folder to a permanent folder once they are satisfied with (or have manually updated) the meta data.
Second comment:
It would be great if MC could save two Thumbnails, and then User could select the best one to display. Perhaps MC would always automatically display the first capture if the User does not make a selection. A lot of times the thumbnail captured is of a commercial or some other scene not very representative of the Show. I set my thumbnail capture time to 45 seconds to miss the intro commercial - but its always just a guess.