Interesting random "fact".
According to the Leichtman Research Group, about one-fourth of HDTV owners in America are unaware that they are NOT watching high definition programming. That is, they own an HDTV and think they are watching high definition TV shows, but in fact are not.
A typical example is the unaware consumer that buys an HDTV, brings it home, plugs it in, and just expects that everything will now be in high def. They see a little "broadcast in HD" symbol at the bottom of the screen while watching Monday Night football and are happy. Perhaps a little confused why the picture quality doesn't quite match what they saw at the store, but they are still happy.
So my advice to all you HDTV window-gazers out there: do your research. Will you need a set-top HD box? Upgrade your Direct TV to handle high def? Subscribe to digital cable? Will an antenna do? Will your Betamax player be compatible?