The plugin formerly known as 'Moviestar' -- Adobe's H.264-capable version of the Flash player -- is now officially released for the Mac (along with Windows and Linux) and downloadable from Adobe's site. Sure, it can play back HD and fullscreen video, but will it reduce the performance hit that Mac users take whenever a Flash movie pops into a browser window? Let you know as soon as we try it.
As our buddy David noted, if you've been running an early beta version of Flash 9 you may want to run Adobe's uninstaller before upgrading.
In terms of the wider online video market, the adoption of the H.264 codec solidifies the QuickTime/Flash axis of power in a big way. Content owners with libraries of QuickTime movies in H.264 now can republish for Flash without reencoding, and YouTube's effort to convert clips for iPhone use now can be leveraged to provide higher-quality Flash playback as well. Big day for Adobe, good day for video fans and producers.