So we may not have to put up with the low quality Flash video at YouTube for much longer. Though it is one of the better codecs for producing high quality video at low file sizes, H.264 is not a magic bullet. But used well, it can offer "good enough" quality for full-screen viewing on a computer without crazy download times.
Adobe has posted one demo. Viewed at full screen, i wouldn't call it high def, but it's sufficient for standard def for today's bandwidths. You can retain the minimal latency of today's Flash video while adding a welcome boost in video quality.
I used to think such intermediate forms of video quality wouldn't be needed for long if Internet bandwidth to homes continued to increase at the rates predicted by Nielsen's Law of Internet Bandwidth. But I feel like Internet bandwidth to the home hasn't improved much for me in the past several years. I'm actually putting up with slower bandwidth here in LA (DSL) than I had a few years ago in Seattle through a cable modem.
True streaming high def over the web is not yet a reality. Someday, but not today.