Three20 is mostly in a bug-fixes only state right now. The fact is that the framework is complex enough that the cost of adding a new feature often outweighs the benefit. This is the main reason why I've decided to start anew with Nimbus and so far the progress has been really great.
Going forward I'm planning to dedicate a chunk of my mornings to working on Nimbus, splitting my time between going over pull requests and building new features. I love building tools to accelerate the development process of other iOS developers and plan to continue doing so for the foreseeable future.