Unfortunately, a tremendous amount of valuable research has been put on hold ever since the ban of federal funding for stem cell research. In the United States, the vast majority of medical research of all types that eventually lead to cures for disease are funded by the federal government. The federal ban on stem cell research does not completely prohibit it, but the effect is nearly the same, just as it would be if the federal government withdrew funding for cancer or diabetes research.
The main opposition to stem cell research comes from the Religious Right who believe that any form of research using fetal stem cells is wrong, because according to their religious views, every fertilized human egg should be considered as much a human being as any living person, even a microscopic zygote consisting of nothing more than four cells of human tissue. Certainly, the concept of religious freedom in the U.S. protects their right to hold those religious beliefs whether or not they make sense scientifically and logically. However, religious freedom also protects the rights of everybody else who may not share those religious definitions of what human life is or when it "begins."
Because the Bush administration is both sympathetic and partial to the Religious Right, current federal law prohibits even the research use of frozen embryos created during in-vitro fertilization (IVF), even though any extra embryos created and left over in the IVF process are just destroyed as medical waste once the couple achieves conception.
That "medical waste" could contribute tremendously to human health and welfare if it were allowed. Admittedly, scientists cannot identify with extreme accuracy a particular instant or "date" when human life "begins" in the womb, but they absolutely can establish minimal criteria (such as the development of a nervous system or a human brain stem) to define a point of gestation before which growing tissue cannot logically be considered alive any more than a small group of any kind of human tissue, such as a mole or a toenail clipping, which both contain our complete DNA sequence that is unique to every living thing. Religious beliefs to the contrary (i.e. that human life begins at conception) have no place outside of the personal choices of those who accept those religious beliefs, and certainly not in the laws of a religiously diverse society.