Pro:
We can bring back dead family members or pets or people important to us.
We can save more lives if we can use stem cells to generate hearts, livers, or lungs for replacement.
It is also believed that we can use stem cells to treat Parkinson's disease, Alzheimer, birth defects, and even Cancer.
Con.
It can be argued that since humans are "creating" life. and also killing life, since a stem cell is taken from an embryo which dies in the process. We CANNOT play God.
That's basically all.