Adobe has just released the new beta versions of Flash Player 11 and Adobe AIR 3 on Adobe Labs. The new runtimes will provide improved performance, support for stage 3D capabilities, native JSON support, high efficiency compression and many other features. You can read a summary of all new features here.
The purpose of this beta release of runtimes is for developers to check that their existing products made using current SDKs work properly on the new runtimes. The SDKs for creating new content is only available for private beta testing at this stage.