Patricia Smith Churchland has famously remarked about Penrose's theories that "Pixie dust in the synapses is about as explanatorily powerful as quantum coherence in the microtubules."
Pretty much. Penrose, despite being generally brilliant, is not an expert in neuroscience. QM explanations seem like hand waving or saying "we don't really know, and since I know a lot about QM, that must be the reason". It's almost avoiding investigation into the hard problems of neurobiology to find the real, physical processes that bring about human cognition.
http://en.wikipedia.org/wiki/Hard_problem_of_consciousness#S...