First off, I must state the obvious. In all these instances we are dealing with a brain deprived of oxygen. And before we start looking for supernatural explanations for this phenomenon, it is well worth seeking a naturalistic explanation, devoid of hocus pocus and wand waving. As in all cases where the solution is not obvious, let us apply the rule of parsimony (Occam's razor), and let us not posit beyond what is necessary. Tis often the case that the simplest solution is the most plausible without a need for a gaudy display and descent into silliness. An abundance, nay a plethora of explanations, is not the rational man's friend. So, having stated the problem, let us delve into this most perplexing conundrum without descending into irrational bollocks.
A Bit of Science (with emphasis on the bit)
It is important to note that personal testament is essentially poor evidence and is certainly non-scientific. Anecdotal reports are not verifiable data and therefore should be dealt with scant regard. A study into the phenomenon of NDEs consisting of 197 cardiac arrest patients found that only 9% of patients had an experience that could be classified as an NDE. Interestingly, Dr. Olaf Blanke of the University Hospital of Geneva (remember him?) was able to reproduce the classical NDE experience in experimental subjects by inserting probes into their cortex. In addition, it has been noted that fighter pilots whilst undergoing training in G force-inducing centrifuges, may on occasion be subject to an NDE- this is due to hypoxia impinging upon the brain under these extreme conditions.
So, in conclusion, currently, we have no evidence that withstands scientific scrutiny of NDEs somehow providing a preview of the 'afterlife'. Proponents who are convinced that NDEs are a foreboding, furtive glance unto the infinite will continue believing so. However, we have no data, to date, that is supportive of their conclusion. Some folk will believe regardless, because they want to even in the absence of supportive data. From my perspective, I find no evidence to support any form of life's continuance once we are pronounced brain dead. Therefore, take pleasure in our brief sojourn on this bittersweet journey that is 'life'. Enjoy, quaff deep, read well, and make love. Converse with the wise and eschew the fool. All else is but commentary, clutter, and noise. Arse.