Elad Elrom at InsideRIA – AIR 2 Enhancements Complete Overview:

"File promises is a new API (URLFilePromise) that allows you to access resources at a certain URL and drag them out of the AIR application as a file promise into the local machine. Once the files are dropped the request will be made to download the file to your local machine.

[…] Adobe AIR 2.0 uses the same branch of WebKit as Safari 4 beta […]. The most significant feature of using this branch of WebKit is the usages of SquirrelFish Extreme (SFX), which has been integrated into the WebKit engine and increases the overall performance of Webkit. "