I just bought an HD TV and HD tuner. There isn't really a great deal of HD content, but some sporting events, like Monday Night Football, are broadcast in HD. It's mesmerizing to watch, almost as if you are there. CBS has the best HD setup, when they use it. Some football games are carried by CBS in HD and it's almost surreal how good it is. They also did the US Open (tennis) and it was spectacular, almost made me want to watch tennis!
Anyway, I chose 2-4 hours but in reality the TV is on much of the day.