I'm near the end of working my way through A Quantum Mechanics Primer, http://www.amazon.com/quantum-mechanics-primer-Introduction-..., and I have not attempted to tackle the PBR preprint, but based on Scott's interpretation of the central point, I don't get the significance of PBR. If two rational people assign different states to the same quantum object, and a measurement reveals an eigenvalue that could only have been associated with one state, and not the other, then one party was just plain wrong. Also, you only get to do one measurement, how does that prove the state was previously pure or mixed? Don't you need a prior knowledge of how the state was prepared to decide that?