It turns out that the high acceleration phase might have some problems. High intensity lasers tend to shred photon sails. I gather the simulation shows that the mass of the electrons starts to become significant in the response of the conductive sheet. The article gives a pretty clear explanation, but the gist is that in order to reflect the light, the electrons in the conductor shuffle back and forth in response to the electric field of the light--but not perfectly. At high intensities the result is that the ions in the lattice of the metal get shaken too much.
So the light sail idea, while it may still work, will probably require lower intensities and a longer acceleration time. Pesky reality has a way of screwing up science fiction plans.