Let's see. 1. It's vitrification, not freezing. 2. Nobody has proposed stitching heads onto random bodies. The idea is to re-grow the lost organs and tissues from the patient's own DNA. As long as the brain survives there is no rational reason to believe a person is truly dead.
It is? I thought scanning and emulation would be a more likely outcome.
I doubt repair is significantly more challenging than scanning and emulation. However it is conceivable that memory loss would be lower with the scan/em method, at least when the tech comes out. In an FAI intelligence explosion event, emulation seems slightly more likely due to conservation of resources. But in the grand scheme of things, a standard human isn't that resource-intensive (compared to e.g. the mass of a planet or a star's total output). I'd say there's a good chance of it going either way regardless of FAI versus incremental tech advancement s...
The BBC News recently ran an interesting piece on living forever. They discuss some of the standard arguments against cryonics and transhumanism; overall, the article is pretty critical of both. I suspect most LessWrong readers won't find it convincing, but it's still worth a quick read.