What makes the Latter-day Saint scheme unusual is not the premortal existence but the ending. Resurrection is universal and unconditional: every person who has lived receives a body again, without exception and without regard to belief. Judgment then assigns the resurrected to one of three kingdoms of glory, and the striking feature is how few people the system leaves out.
The celestial kingdom is the highest, reserved for those who received the ordinances, kept their covenants and were sealed in eternal marriage; its highest degree is exaltation, in which a couple continue as a family and continue to progress. The terrestrial kingdom is for the honourable who did not accept the fullness, and the telestial for those who lived without law and were not redeemed until the end of the millennium, but even the telestial is described in section 76 as surpassing all understanding. Only a very small number, called the sons of perdition, who knew the truth in an unusual and direct way and then denied it, are placed in outer darkness. There is no eternal fire for the ordinary unbeliever, and there is no infant damnation: the Book of Mormon condemns the baptism of children in terms rare for a nineteenth century American text.
The demanding half is at the top rather than at the bottom. Exaltation requires ordinances that most of the human dead never had the opportunity to receive, and it is that gap, rather than any anxiety about hell, that drives the movement's enormous investment in genealogy and in proxy ordinances. The doctrine sets a low floor and a high ceiling, and almost all of the church's ritual effort is directed at the ceiling.