Whilst this is a new codeplex project, it has actually been used privately throughout several commercial projects, so has a good amount of maturity and debugging already behind it. As of first commit though, there is some tidy up and refactoring yet to be done before I am satisfied with giving it a "1.0" label.
Currently there is no support for JavaScript; it is purely and simply HTML-based with session/cookies persistence, GET and POST operations, HTML parsing and an internal LINQ-to-XML-based document querying system.
There is much to do but it is certainly usable in its current state.
Please expect breaking changes in future releases.
Read more: Codeplex