It did not take long for a skeptical critique of Dr. Eben Alexander's "Newsweek" article promoting "Proof Of Heaven" to manifest... Victor Stenger lays out the classical scientific / materialistic rebuttal in today's "Weird News" section of Huffington Post.
What Stenger takes issue with--and he's probably right--is Dr. Alexander's characterization of his NDE as being proof of "Heaven," and particularly, of "God." Any Christian fundamentalist will tell you that there's no room for God in science--not because science doesn't believe in God, but because the existence (or non-existence) of God will never be proven by the current scientific method.
I noticed Dr. Alexander's rush to explain his NDE in religious terms, knowing that critics would attack his religious interpretation, rather than the experience itself, although I don't think that it should skew his narrative, and it personally did not bother me. (For an example of a book along this theme that *did* bother me, take a glance at Dr. John Lerma's "Into the Light: Real Life Stories About Angelic Visits, Visions of the Afterlife, and Other Pre-Death Experiences." This book is so demagogically Christian as to be offensive, to the point that I doubted whether any of it was true.)
Stenger's critique is important, however, because it shows how difficult it will be for science to examine NDEs. In Stenger's weltanschauung, reality is defined as what our physical senses, and what our physical instruments, can perceive. We absolutely cannot measure what we cannot perceive. We can infer the existence of an "afterlife" by collecting accounts of individual experiencers, and we may be able to mathematically theorize it, but that's all we can do--at this stage, anyway.
Dr. Alexander's account, however, is not really about validating his NDE to the scientific community; it's about describing a remarkable experience involving an expansion of consciousness, where nonphysical realms *were* perceived. And I think that this is where science will eventually go. At some point, a light will go off over a scientist's head, and he will realize that the goal of science should not necessarily be to study what we already can see--but to see where we currently can't.