I bought an HDTV a month or so ago now, and at least on Time Warner Cable in NYC it seems not everything on the HD channels are actually broadcast in HDTV.
There doesn't even seem to be a pattern that I can figure out as to what is and what isn't broadcast in HD. In some cases, older movies and shows are in HD while new ones aren't. Sometimes daytime and/or late-night is in HD while prime-time isn't.
For example, CBS broadcasts StarSearch in regular format at 8pm, CSI: Miami in HD right afterwards, and then Letterman in regular format.
NBC does the opposite - most of their primetime programming, like Friends for example, is broadcast in regular format, yet they broadcast Leno in HDTV.
For the Superbowl, ABC went back and forth between HD when there was a timeout or other stoppage, and the pre-game wasn't in HDTV.
HBO seems pretty good about HD, but then with their original series I'm confused. The first season of The Sopranos - a repeat, and filmed 5-6 years ago - is being broadcast in HDTV on Sundays, while their new programming - Oz and American Undercover - are not, which leads me to believe it's not just "how it was taped" either.
Can anyone point me to some real reason - economic, technical, whatever - on why this happens? Is it really that expensive to broadcast something in HDTV when the infrastructure is already in place?
Hopefully whatever these reasons are will be mitigated over the next year or so, because watching HDTV is really unbelievable. I never thought there would be such a difference... but when going back and forth it's really amazing.
I just can't wait for more programming - ESPN-HD is going to be nice. I would LOVE the rest of the HBO package in HDTV. What really amazes me - and I guess there's some technical reasons for it - is that they don't have the OnDemand channels in HDTV yet. I know I definitely would use it instead of renting DVDs, since it's convenient and the quality is better - even if I can't get the absolute latest movies.