There's not yet evidence in favour of brain function being preserved though, even if the structure seems somewhat intact.
Anyway, many electron microscopy studies show that even in ideal laboratory conditions, cryoprotected tissue always has some amount of freeze damage to its structure, despite some areas being beautifully preserved. Humans have it even worse than the average lab rat, as there is always going to be a greater amount of post-mortem delay - during which the brain is undergoing ischaemic damage.
Cryonics is an interesting area of research, but the claims of being able to preserve memory and personality are really quite unfounded at this point.