Adobe has released stable update of Flex 3 SDK and FlexBuilder.

Flex SDK 3.2

* Numerous bug fixes including fixes provided by the community.
* Support for Flash Player 10.
* Support for Adobe AIR 1.5.
* Support for sandboxed and multi-versioned applications. Flex 3.2 adds the ability for an application developer to divide functionality between multiple sub-applications and allow them to interoperate. Applications can be developed using different versions of Flex (starting from 3.2), and can optionally operate in an untrusted environment which allows applications to safely load code provided by third parties. For more information, please refer to the related documentation.

Flex Builder 3.0.2 (including the data visualization components)

* Numerous bug fixes.
* Support for Flash Player 10.
* Support for Adobe AIR 1.5. The default settings for Adobe AIR 1.5 will enable Flash Player 10 functionality in Adobe AIR.
* Support for QTP 9.5 testing against IE7.  Previously only QTP 9.2 was supported.

Devnet: http://www.adobe.com/devnet/flex/articles/sdk32_fb302.html
download the Flex Builder update from here,
downloading nightly or stable builds from the Flex SDK Open Source site