As part of the 300 program, Steorn recently released specific details about their technology, which was pretty much the whole point of the 300. The general reaction has been vaguely positive and appreciative (like this posting), though there is a huge self-selection bias in play.
Their key operating principle is clever and unlike anything I’ve seen in my armchair studies of supposed magnetic motion machines. But it’s complicated, in a way that is like the EM equivalent of the three-body problem. In other words, their description is neither obviously wrong nor right. Any time you have moving magnetic fields and pulsating electromagnet currents, hard-to-predict interactions tend to happen. There’s also a host of measurement difficulties, including properly accounting for power factors and complex number phasors for power input/output in inductive circuits.