The newest official release of the Flex SDK, version 3.3, is out. It's a solid upgrade and you can get it at:
If you use Flex Builder, be sure to download and add the Data Visualization components to your 3.3 SDK (can't use the Advanced Data Grid and other, related, classes without this). It's a separate link at the same URL as noted above.
I don't think I can say too much (have to check my NDA) but I've been given an opportunity to start testing the next version of Flex and Flex Builder (code-named Gumbo). I won't post any details on it now (until I verify what I can and cannot say) but it looks AWESOME...and this is just on the Alpha version. The data centric nature of the forthcoming version is going to make a lot of developers, myself included, happy.
Be sure to upgrade both AIR (1.5.1) and Flex (3.3) to the newest versions. Plenty of good bug fixes and some nice new features.