The resolution of the Peachy is a tricky thing, because it's analog rather than digital. It has a measurable precision, but that can change drastically based on the software (which is still changing quite a bit) and the clarity of the sound card used. Possibly even the quality and shielding of the cable, being able to actually see sound quality as a physical object can really turn someone into an audiophile.

Also, the laser currently has to be calibrated by eye, meaning the overall scale would be hard to get better than +-.5mm, but details smaller than that would still show up if you have the sound quality for it.