He says cryonicists would first have to learn how to freeze a live healthy mammal for a long time, then thaw and revive it. Then they would have to cure whatever disease a would-be cryonaut had died of. And they would have to bring a dead person back to life. I solicited comments from various individuals, including several cryobiologists. In general, the cryobiologists most critical of cryonics had little or no knowledge of nanotechnology.
Feasibility is the fundamental issue.