Alcor says:
"It is a well-established fact that long-term memories are encoded in durable physical and chemical changes."
Usually the problem is not with freezing - but with thawing. Vitrification improves things further - but even without that an enormous quantity of information seems bound to be preserved. I don't think scepticism about this has much scientific basis. We know enough about the brain, and about freezing to see that a mountain of information will be preserved.
Also, check out the frozen frogs.
I recently found something that may be of concern to some of the readers here.
On her blog, Melody Maxim, former employee of Suspended Animation, provider of "standby services" for Cryonics Institute customers, describes several examples of gross incompetence in providing those services. Specifically, spending large amounts of money on designing and manufacturing novel perfusion equipment when cheaper, more effective devices that could be adapted to serve their purposes already existed, hiring laymen to perform difficult medical procedures who then botched them, and even finding themselves unable to get their equipment loaded onto a plane because it exceeded the weight limit.
An excerpt from one of her posts, "Why I Believe Cryonics Should Be Regulated":