Yes - it is finally out. The beta version of Adobe Flash Player 9 for Linux is now available on Adobe Labs, at http://labs.adobe.com/technologies/flashplayer9/.
Additionally, the Flex 2.0 compiler for Linux is available. The Flash Player 9 Update Beta for Linux includes the features of Flash Player 9 Update, with the exception of full-screen mode and SSL support (SSL support is currently available in the Linux Plugin but not the Linux Standalone Player). Full-screen mode and SSL support will be available in the final release. We've also posted a Linux Beta FAQ on the Flash Player wiki on Adobe Labs.
Now you can develop and test on your Linux machine. Use the free Adobe Flex 2 SDK , which includes the command-line compiler to develop and deploy Flex-based applications entirely on Linux machines. Flex Data Services is also supported on Linux. More info here on the Flex 2 for Linux wiki on Adobe Labs.
And, because this will be the next question now that we've satisfied your beta player needs: the Adobe Flash Player team is working on support for 64-bit platforms as part of our ongoing commitment to the cross-platform compatibility of Adobe Flash Player. We have not announced timing or release dates.
Known Issues - Linux
* Full-screen mode is not available for the Linux player yet. This feature will be implemented for the final release.
* SSL support is not available in the Linux Standalone Player. This feature will be implemented for the final release.
* Express Install is an unsupported feature due to the variety of Linux platforms, each handling the Adobe Flash Player plug-in installation in different ways.
* The plugin does not currently work in Opera browsers. We are working with Opera on these issues.
* Artifacts may appear when video initially plays.
* System fonts may appear differently between Linux distributions. Formatting issues may result.
* AMF3 connections do not work over RTMP. (186958)
* Right clicking outside of Flash Player while the context menu is displayed doesn't make the context menu disappear. Workaround: Left-click to turn off the context menu. (187957)
* IME is not available (no international text input). (184489)
* Acrobat Connect Add-In installation is not working at this time. (188318)
* The Standalone Player is available in English only. (184237)
More info on system requirements and fixed issues for Mac and Win in the release notes. You should also check any detection you've built for your demo sites -- we fixed the problem where the first beta was 9.0.18.x but we had already released the Intel Mac version as 9.0.20.x. Sorry about the confusion. Now Update 1 has been bumped up to 9.0.21.x across all available platforms.