Instinctively, I feel this technology is wrong. I would not use it and would disapprove of anyone who did. However my personal revulsion is no reason to want a law against it (as we have at present). There are many things I find revolting which are (or should be) legal.
After many years of infertility treatments, research is now beginning to show (as I would have predicted) that the children of infertile couples are more likely to have health problems than those of parents who conceive without scientific intervention. Sometimes there is a good natural reason why a couple can't conceive, which it is morally wrong, or at least highly irresponsible, to ignore. Sometimes one or both parents could conceive easily with someone else, but together they simply represent a poor genetic combination. My children have been the greatest joy in my life and I feel very sorry for any couple that can't conceive, but in their place I think I would accept Nature's harsh verdict. I would think it better to give a loving home to a child in need of adoption, than to risk producing one of my own to suffer.
Of course, in these uncomfortably mystical terms, Nature has given no verdict on the capacity of same sex couples to reproduce. They may both be perfectly capable of conceiving with a wide range of partners. Perhaps there is less reason to object to their conceiving by artificial means than there is for infertile heterosexuals? However, any combination of genes untested by Nature represents an increased risk which I would not personally take.
In the end, it's impossible to legislate sensibly for these matters. The drive to reproduce is so powerful that many couples will take the risks of genetic defects. If their country bans a technology, they will travel to another to use it (or they will simply do it illegally). Scientists are far more driven by curiosity than ethics, so there is no effective way to legislate against such research. The idea of legislating against knowledge disgusts me anyway! Some same sex couples will be eager to use this technology in order to make a political point. I fear for a child conceived for such a reason, but many are conceived for much worse (or none).
My ethical problem as a libertarian is this; while I am all for being able to take risks for myself, I struggle with the notion of taking them for an unborn child. In such cases it is the child who will live with the consequences of the parent's choices. What do you think?