Note, this is my unfiltered opinion:
Ethics schmethics, who gives a damn? This is a fantastic scientific advancement, and I always cringe and get pissed off when people start shouting "unethical" over things (of which this falls into the category of) that do not impart harm or stress on individuals. Like with other fertilization methods, and other things related to stem cells, the common argument is "you can't play god". Uh, why not? That isn't a reason to not do something, that's just someone being upset over the idea that we can control something that nature is naturally able to do. We manipulate nature on so many levels all the time. Sometimes that statement comes from a religious standpoint too, which has absolutely no bearing or play into this at all and can't even be used as an argument for or against it.
A somewhat more valid concern is a "slippery slope argument", but honestly I find nearly all slippery slope arguments in any context to be invalid. How often do you see a true slippery slope scenario actually play out? Hardly ever. Just because we do something now, doesn't mean we aren't going to be able to individually evaluate and assess a new case or breakthrough. While it seems similar to eugenics in the right light, this isn't even close to that. This is about two individuals deciding that they want to have a child. The difference, it's being made in a dish initially from stem cells. It's simply a new kind of test tube baby. This isn't going to make the idea of "designer babies" more or less likely, but that's another debate.
Looking around I've seen a few people say "people should adopt". Oh for the love of god take your moral high horse put down and grow up. It strikes me as just the same as people who get mad at you because you didn't adopt a pet. Yes, there are children who need a home, but taking on a child is a huge deal. Parents have the right to decide what kind of child they want, and if they want one of their own. It's nothing more than a guilt trip for not taking the lowest common denominator. Adoption is not for everyone.
Some will say "just because you can, doesn't mean you shouldn't". As I see it though, when it comes to scientific research, if you can remove elements of harm, I say "Just because you can, means you should". This is how we advance, progress, and discover as a society.
As I see it, I don't see a single valid argument against doing this. This has a very high chance of giving benefit and advancement, and a nearly nonexistant chance of causing harm.