Watch the samples here.

The samples use 4 different videos. The movie trailers are all from Apple.com while the Backcountry clip is from Adobe. The trailers all use H.264 video in 720p resolution (1280x720), however the Shrek trailer is quite dark. Make sure you hit the full screen button. My 2.21Ghz Vista machine really seems to struggle, but it struggles with .MOV also. Also note that I haven't implemented any of the performance tips which Adobe recommend. Be patient, each video is between 50MB and 100MB in size. It's using a 10 second buffer - not recommended for dial-up :-) If things seem slow now then please try again later.

A heads up: the FLVPlayback component will currently not accept files with a .mp4 extension. I had a hard time getting it to work and had already rolled another player when I tried simply appending .flv to it. That did the trick and my mp4 files now use a naming convention of Rendition.mov.flv, even though it complained that the file can't be opened. trust me it can once you run it in a browser. I am sure this will be fixed in a future update for FLVPlayback.
The Flash Player simply ignores the file extension (once the file is loaded) and figures out the contents by itself by looking into the file. So even though it says .flv on the outside it's got H.264 inside. Note also that watching of videos does not seem to work inside the Flash IDE, presumably it is using an older Player there.

Lastly I am making my FLA file available for download. You need Flash CS3 to open it.

Have fun. If my site goes down later today you'll know why :-) Donations in form of a CDN account for downloadable content are most welcome.

There's some more great info on H.264 here.