I've heard about it but near as I can tell it's still very much in the lab phase, and I'm not clear on just how strong the actuators are. Human leg joints need to be able to put out an astonishing amount of torque at pretty high rotational speeds sometimes.

The future will probably be some sort of artificial muscle derived actuator, absolutely. But for now the only way to do anything useful with a humanoid robot is with hydraulics (Atlas), huge electric motors that are either too slow or water-cooled, or sacrificing capabilities to focus on just a few things (Cassie)