One of the biggest problems we find on most computer vision libraries is the fact that a lot of knowledge in the area is required to use them properly. We think the complex APIs that are exposed to developers that try to make CV apps can be the reason why we still don't see many apps exploring the potential of CV. So tracking.js was created with the goal of being as powerful as the best CV libraries, but without exposing the inherent complexity of the area to the developers that wish to use it. From what I saw of jsfeat, it looks very powerful, but targeted for people that have some knowledge of CV.