The official announcement on the Digital Media blog:

Today, we released the latest version of the Flash and AIR runtimes with Flash player 11.4 and AIR 3.4. These new builds feature a few great features that gaming fans will be excited about; most importantly, we’re increasing the devices that can take advantage of hardware acceleration so game developers can give more gaming fans smoother and more exciting game play.

Along  with adding constrained Stage 3D, we’ve also provided added support for iOS application development, and introduced concurrency, which helps improve game responsiveness. Gaming evangelist Lee Brimelow will be walking users through the new features and upcoming tooling updates in a demo on August 23. [more on the Digital Media Blog]

Concurrency (ActionScript Workers) — This feature enable developers to off-load certain tasks like high-latency operations and long-running computations to “workers”. These background workers run concurrently in order to leverage more machine resources and avoid things like UI freezes and allow content to be more responsive.

Stage3D constrained mode — A new parameter to Context3D has been introduced called “constrained profile”.  Constrained profile allows Stage3D content to run hardware accelerated on more hardware, especially the Intel GMA chipsets. The Starling framework has been updated to be constrained mode ready.

StageVideo.attachCamera — Provides webcam support for StageVideo. This allows developers to leverage GPU acceleration to render webcam video streams.

Camera.copyToByteArray/Camera.copyToVector — Allow efficient copy of the video frames pixels to an existing ByteArray or Vector.

LZMA support for ByteArray — In addition to zlib compression of ByteArray, we are introducing an additional compression type based on LZMA to compress data inside a ByteArray through ByteArray.compress() and ByteArray.uncompress()

Update Flash Player and Adobe AIR.