Another vote for a modern WebKit.
We have a web app that uploads video files directly to YouTube. To do this it uses HTML5 features: XHR2, FormData, FileList, and Blob. When this app is loaded via AIR it doesn't work because those features aren't available. The AIR environment isn't available either since it is loaded via web request. So the problem we have is how to develop modern interfaces and interactions using an old browser environment. We don't want to have two code bases, one for customers using the web site and another for customers using the AIR app.