The first time I watched a television program broadcast in HD (I believe my first was CSI: Crime Scene Investigation), I knew I would never be able to go back to SD unless there was no alternative available. And I've found that an HDTV actually accentuates the flaws in an SD broadcast (blockiness, false contouring, fuzzy quality instead of razor sharpness).
But, I do know that other people who enjoy TV as much as I don't have as discerning an eye. My neighbors had had their HDTV for about four months and called me over to calibrate it (I really think they wanted to show it off since it was a 70 inch screen and mine wasn't that wide). They were watching a college football game on ABC, but they weren't watching ABC-HD but rather the standard ABC channel with the 4:3 image stretched to fill the 16:9 screen (and they thought that was the way it was SUPPOSED to look!) After showing them where the HD channels were on their cable box, you should have heard the ooohs and ahhhs. They had NO idea they weren't already watching HD. After the calibration, I brought out the Blu-ray player and put on THE SEARCHERS. Mike (the neighbor) went and bought a Blu-ray player the next day.
But, I do know that other people who enjoy TV as much as I don't have as discerning an eye. My neighbors had had their HDTV for about four months and called me over to calibrate it (I really think they wanted to show it off since it was a 70 inch screen and mine wasn't that wide). They were watching a college football game on ABC, but they weren't watching ABC-HD but rather the standard ABC channel with the 4:3 image stretched to fill the 16:9 screen (and they thought that was the way it was SUPPOSED to look!) After showing them where the HD channels were on their cable box, you should have heard the ooohs and ahhhs. They had NO idea they weren't already watching HD. After the calibration, I brought out the Blu-ray player and put on THE SEARCHERS. Mike (the neighbor) went and bought a Blu-ray player the next day.