At one time organ transplants were considered an ethical grey area (perhaps they still are by some), but I think most people now would consider it better to save lives in such a manner when it only brings help to those who need it and it's possible to, compared to the alternative. Having the capability may mean that things like organ theft now exist, but the benefits around the world outweigh the nastiness that has always come as part of human nature.
I agree that organ transplants are a net positive, and in fact are far less susceptible to unintended consequences (there's a pretty low limit to the number of organs and operations involved, for one.)
I also think that gene repair is a net positive. I would just like us to, for once, look ahead and foresee some of the foreseeable consequences and act to mitigate them before the bulk of the damage is done.
I don't think it's necessary to slow the development; gene therapy is too desperately needed, and slowing it down so that we can prepare is not going to cause us to prepare.