I would say it's probably no higher than 0.1%.

But by no means I'm arguing against cryonics. I'm arguing for spending more resources on improving it. All sorts of biologists are working on longevity, but very few seem to work on improving vitrification. And I have a strong suspicion that it's not because nothing can be done about it - most of the time I talked to biologists about it, we were able to pinpoint non-trivial research questions in this field.