The probablility of success is unknown.
Something is known about it, and correct decision depends on its value, so by making a decision you implicitly estimate its value. See I don't know, logical rudeness and Scientific Evidence, Legal Evidence, Rational Evidence.
Yes, I certainly do know things about cryonics. I know it is a process where those who are currently considered deceased can have their bodies preserved at extremely low temperatures. I know this is done with the hope of reviving those people in the future. I recently learned that I could probably afford it, which was not something I knew before. I also recently learned that cryonics techniques preserve more fine detail than they once did. In fact, both of the things I learned push up the probability that this procedure might be useful to me. Unfort...
From Mike Darwn's Chronopause, an essay titled "Would You Like Another Plate of This?", discussing people's attitudes to life:
Conclusion, graphs, and references in article. As usual, I recommend reading Chronopause.com as Darwin has many good articles; to quickly link a few: