I like that it's a relatively easy way to get started writing tests, and that the documentation is very good. It's free! There are some things (such as getting tests running) which seem to require a little bit of manual work, but overall it's been quite straightforward. It took me about two weeks to learn how to use it properly. That said, there's a lot of room for improvement in terms of usability. I would recommend using this as part of an automated test suite. I've found that it makes it easier to write tests by giving me a skeleton implementation.