[littlemanpoet]

Death, as defined by Christian theology, is separation from God.

When Adam and Eve fell to temptation, according to the mythology (true myth for those who wish to see it that way), they became "dead in sin". That is to say, they had begun to suffer separation from God because they had done what God said they must not do.

The cessation of physical function in a human is the physical manifestation of Death. The non-physical manifestation (if one may call it that) is the soul's/spirit's experience of reality as apart-from-God. To any who hunger for God, this is tantamount to eternal starvation rather than salvation.

The Death as described above, is what the Someone changed about 2000 years ago.

So Death is no gift, understood in this way, could never be, and is not, I think, what Tolkien is talking about. I don't think he meant the cessation of physical function as the Gift of Death to Men. Nor do I think it's mere release from the trammels of this life.

The Christian view looks forward to a New Heaven and a New Earth, in which human bodies and spirits have been re-created to live, in-God, for eternity. Perhaps the gift Tolkien writes of is nothing more, nothing less, than the hope for something more beyond the circles of Arda.