[T]here is great reason to hope that death is a good, for one of two things: - either death is a state of nothingness and utter unconsciousness, or, as men say, there is a change and migration of the soul from this world to another. Now if you suppose that there is no consciousness, but a sleep like the sleep of him who is undisturbed even by the sight of dreams, death will be an unspeakable gain.... But if death is the journey to another place, and there, as men say, all the dead are, what good, O my friends and judges, can be greater than this? ... What would not a man give if he might converse with Orpheus and Musaeus and Hesiod and Homer? ... Above all, I shall be able to continue my search into true and false knowledge; as in this world, so also in that; I shall find out who is wise, and who pretends to be wise, and is not.
-Socrates, from Plato's Apology
I once had a professor of philosophy who was very interested in Near Death Experiences. These are the things you hear about where the brain is approaching death, and visions of light or transportation occur. I've had one myself, in fact, when choked out of consciousness for a minute or two by my old master of jujitsu. These things are kind of interesting, in a way, because they are often quite similar in spite of cultural differences or other inputs. They don't, however, speak very much to what it is like to be dead, even "brain dead." This is because we can't be sure that there isn't brain activity of some kind.
Recently, though, I've come across two people who present empirical accounts of long-term "brain death" -- we really mean a coma in both cases -- which were monitored in hospitals. They are really different sorts of accounts.
Gerard at American Digest gives this account: the lights went out, and then flipped back on. For the intervening 13 days, there was nothing at all: not even a darkness, not even sleep, just nothing.
Dr. Eben Alexander, a neurosurgeon who was comatose for eight days, gives an entirely different account: one of transportation, and beings of light, and a kind of maximum being that is not light but not yet darkness. There is emotional content: love, joy, and not so much forgiveness as the sense that there is, and can be, nothing to forgive.
Which account you find more plausible depends on your own assumptions, but from a scientific perspective it doesn't matter. What we have here are two roughly analogous events, with a surprisingly different phenomenal content. The first one lines up with what is suggested by what we think we know about the brain; the second lines up with numerous other empirical accounts of near-death from around the world.
None of this actually speaks to the real question, which is what it is like to be dead. There also remains enough shadow in our understanding of the brain that even with brain scans you might hope that the brain-only account can yet 'save the phenomena.'
Still, how interesting the difference.