Well, without some sort of working theory for what happens, we're left to gauge morality based on the results of this life.
Without such a theory, there's no reason to adopt the sort of transcendant moral posture that seems to drive the objectivists. Indeed, objectivists' theory ("this life and you're done" ) much demands that morality boils down the old bumpersticker: "He who dies with the most toys, wins."
Note that there are no particular rules mentioned for how one gets those toys -- if you manage to die old, rich, and happy, you've won.
What it reduces to is a pragmatic approach, such as general_re has described in this thread, to the effect that on average, people who behave well will do well. Unfortunately, pragmatism doesn't preclude the mafia don or murderous Pharaoh who, by "getting away with it," can be "winners" in the same sense as an honest man. We can say it's wrong -- but really we can only justify retaliation based on our communal dislike for what they do; we have no objective basis for saying it's wrong.
For transcendant moral values to have any meaning at all, they must have some consequence beyond our lifetime. In the "evolutionary approach," the consequences may be an inability to pass on our genes. From the Christian perspective, we know we will be judged.
Ironically, the objectivist self-interest angle seems to be one of those which logically cannot support the existence of those transcendant values it claims to have derived. It simply cannot answer the question of why the happy Pharaoh is wrong.