FUEL 0.1 landed on the trunk yesterday. Progress had slowed since the last update mainly due to John and I having so many other balls in the air. For those intrepid enough to play with 0.1, you can use the API on the wiki and the code in the unit tests as examples.
The wiki has the plans for 0.2, which should have more features for extension developers to use. The Browser and BrowserTab helpers alone should make life easier.