I recognize this is an old post, but I just wanted to point out that cryonics doesn't promise an escape from all forms of death, while Heaven does, meaning Heaven has a much higher burden of proof. Cryonics won't save you from a gunshot or a bomb or an accident, before or after you get frozen. Cryonics promises (a possibility of) an end to death by non-violent brain failure, specifically old age.

Science has been successful in the past at reducing the instances of death by certain non-violent failures of various organs. Open heart surgery and bypass surgery are two important ones, but there's also neurosurgery to remove formerly fatal brain tumors, hemispherectomy to cure formerly fatal epilepsy in children, and various procedures to limit the damage and reduce the lethality of strokes.

Add that to the fact that we know scientists are continuing to study the human brain, and there's no reason from the inside or the outside view to think that they'll suddenly stop, or that they'll find that old age is the one brain disease for which there's nothing that can be done even in theory, and there's reason to assign a small but non-trivial probability that if humanity survives for a couple of centuries, old age will be yet another formerly fatal disease that science has cured. That reference class is quite large, and the reference class of science doing the impossible is even larger (see flight, space travel.)

As for artificial intelligence, what about the reference class of "machines being able to do things formerly thought to be the sole domain of humanity"? Chess-playing computers, disease-diagnosing computers, computers which conduct scientific experiments, computers which compose music...I'm sure I'm missing many interesting innovations here.

ETA: A better rerefence class would be "machines doing things that were formerly thought to be the sole domain of humanity, better than humans can." Chess playing computers and calculators would fit into this category, too.