In a previous post about the differences, I don't want to dismiss the importance of actual challenges beyond semantics. To summarize, here are key doctrines of Mormonism that seem to contradict assertions of transhumanism:
1) Eternal Life requires spiritual obedience to commandments and God's grace and forgiveness, not advanced scientific discovery: Doctrine and Covenants 14:7: "And, if you akeep my commandments and bendure to the end you shall have ceternal life, which gift is the greatest of all the gifts of God. (Also D&C 6:13)
2) Resurrection is a result of, and patterned after Jesus Christ's resurrection, not man's scientific work, as I have already discussed in my doctrinal and logical response.
3) Final, Eternal Judgement based on benevolence or love for others, but also on proper performance of certain ordinances given by those with proper priesthood authority.
If, as transhumanism seems to suggest, the final, eternal judgment doesn't matter or won't require dramatic, powerful intervention after we die, then why do we need obedience to certain commandments or ordinances, such as baptism, temple marriage, etc., that really have very little to do with increased benevolence? Sure, baptism is a covenant to essentially be benevolent ("mourn with those that mourn"), but becoming benevolent posthumans certainly wouldn't require full immersion and certain proper words spoken by someone who has proper priesthood authority. (See 3 Nephi 11:24-38).
Overall, as I see it, the difference comes mostly to a matter of pride.
The transhumanist emphasis on man's work is a remarkably proud proposition that suggests we don't need God and that his commandments are not necessary or relevant. If we can resurrect ourselves--or, incredibly, even grant ourselves forgiveness, eternal life and future creative ability--through scientific progress, who needs God or His commandments or ordinances?
Since pride is the "universal sin" and "The great stumbling block to zion" that scriptures and modern prophets have repeatedly warned against, I'm more concerned that we have a tendency to become too proud, than that we might have a tendency to discontinue our interest in scientific discovery. Plenty of worldly pressures will encourage scientific progress to continue, regardless of religion.
However, few forces exist other than scriptural and prophetic warnings to restrain the unbridled pride that can lead to our downfall. So, in my religious practice and belief, I'd rather emphasize our dependence on God instead of our ability to do everything, including resurrection and eternal life, by ourselves with our own ability.
Of course, that doesn't at all dismiss our need to work diligently to protect and preserve the earth, find cures for diseases, help the poor, etc.