My HTPC is the only device connected directly to an input on my TV. It doesn't even have a coax cable, cable box, or any other devices attached.
MC is the primary media front-end I use for entertainment purposes.
The only real exception now is for Live TV viewing, for which I still use SageTV.
PS. Live TV basically only ever happens for Sports, and since I'm not a huge sportsball guy, and the Olympics aren't this year, and it isn't a World Cup year (I do like Soccer, as we call it here, but it is hard to follow closely here except for during the World Cup)... That basically only happens when my friends come over and say "Hey, turn on the X game." So, I fire up Sage and ask what channel to put on.