Did you mean to say "computer plugged into your TV"?
Not permanent, but we do it often. I logon to Motogp to watch a race or Amazon streaming to watch a movie. Very useful.
We're considering doing it full time... Cut the cable, and entertain another way.
Oh - you mean totally. I've know folks who have done that. I have a couple of shows I love to watch, but I think they're always available right after airing. Cable is way too expensive, I have to admit.
Ya, cable is a bit silly these days... so are the dish competitors.