You should listen to some of Fyodor's lectures in Microbiology, which are available here on iTunes University for free. Especially, listen to "The Recombinant DNA Debate", where he walks through the history of rDNA and the opposition. By the end he is on fire, it's one of my favorite lectures to listen to.
If the whole bone marrow is removed in an ablative treatment (rather than a partial fashion), some of the clinical risks of the treatment remain. The big two risks with bone marrow transplants are 1) rejection of the new marrow and 2) infection, as the immune system is suppressed while the marrow regrows. Using one's own marrow with largely one's own DNA should (?) eliminate the first to a large degree, but the second still remains.
In the case of the latter, I talked to one of the researchers who worked on this project. A thing they mentioned was that, after breaking and rejoining the DNA, you don't necessarily need to screen the stem cells for those that integrated the corrected fragment. Once in a human body, at least in the cases of β-thalassemia and sickle cell anemia, there is a selective advantage for the modified stem cells.