Yeah, I freeze and thaw cells constantly without much trouble--just plop those suckers in a solution of 10% DMSO and a serum-containing isotonic liquid then throw into the freeze-assist device, then put that into the -80C freezer and transfer it to the liquid nitrogen freezer the next morning. Everyone does it this way, and has for years. I've always wondered if the freezing and thawing process subtly changes cell functioning (beyond the time given to cells to rest after being thawed), but I'm guessing if it were the case someone would have noticed it by now.

The bugger that haunts human cryonics is that thawing is never perfect because the cryoprotectants used to prevent ice-crystals within the cells are usually toxic. If you freeze cells that are measured to be 100% viable/alive at the time (very common) then thaw them using best practices, you're going to have some cell death-- maybe 1-5% if you're fast (less time spent in toxic cryoprotectant) and lucky. If you're unlucky or slow, you can look at 25-45% of your originally healthy cells being dead upon completion of the thawing process. The remaining cells are usually extremely discombobulated, and can take days to return to their baseline. This is completely fine if you're tooling around in a research lab or industrial lab, but even a 1% loss is probably too much for a human brain to bear and remain the same as before.

I suppose that if you work under the assumption that the future technology cryonics relies on for thawing will exist, cell loss during thaw will not be a problem; I find this possibility to be fairly likely over a long time span. Alternatively, you could assume that there will be advanced ways of restoring brain function or generating fresh neurons after systemic damage-- quite a stretch if you ask me, but it's conceivable. I think that ultimately the goals of cryonics will be scientifically realizable for those who were most recently preserved.