It's great to see that someone has finally tackled this feature for WordPress, and my testing thus far suggests that they've done a nice job of it. It's a big win for users to have their developers be able to do this sort of automation without writing custom PHP that someone is obliged to support forever. A rules scripting system like this provides a level of abstraction that, in addition to simplifying the implementation of many features, can considerably reduce the ongoing support burden associated with them.
For this system to achieve its potential, other plugin authors will need to step up and provide integration support for their events and data. I hope that they will. The API provided to permit this looks pretty clear and complete.