I was thinking that it would be very nice if the "Watching" list could be expanded to alert you when a new episode you are watching is released.
Kind of like combining the "Watching" feature with a Subscribe type feature. To be honest, that is what I was expecting to happen when I added shows to my Watchlist.
I think that would be a common sense addition that would greatly improve the user experience.
Along with that, it could be expanded to send email or sms notifications if someone wanted.
Another feature would be to automatically "scrobble" (as last.fm would put it) the shows youve watched.
This could be the foundation for a broader recommendations system based on users with similar tastes as your program list expands.
Just some thoughts.