The only project actively using it at the moment is https://cupcake.io (for example, my profile is https://frabrunelle.cupcake.is).

This is because Tent app developers are waiting for Tent 0.4, which contains several new features (https://github.com/tent/tent.io/issues?direction=desc&labels...). It should come out in a few months. The team behind Tent is currently focusing on https://flynn.io, which they are about to launch. Flynn is important for Tent because it facilitates the deployment of Tent servers.