Maybe everyone posting above are correct with regard to "the 1080's". The format that is generally accepted as "the best" is 1080p because of the alignment of it's screen refresh rate with the source of the signal, resulting in a less "jerky" picture. It's the 1080p format that uses tremendous amounts of bandwidth and is unlikely to be broadcast anytime soon. But posters above are correct in noting that a few stations are providing a signal in the 1080i format, which is more manageable as far as bandwidth is concerned.
I should have been more specific. Check out the following C-Net article explaining the differences between 1080i and 1080p.
http://reviews.cnet.com/4520-6449_7-6361600-1.html