I definitely agree with Satya, that many other things are more important than gender of the parents. Sadly, most people are really ignorant (or is it just that I live in Arizona and am surrounded by them....?).
However I do not think that we can ignore all psychological and sociological studies, as there are many parameters to in ensure their correctness. We should thoroughly explore the study and if we cannot, then take the info with a grain of salt.
I actually read a study (a real peer-reviewed scientific article of a study with all the parameters and statistics laid out, not just an article pulling from the findings) and it said that children of lesbian couples (they, sadly, did not include gay couples, only lesbian and straight, of different places and classes) tend to have far less anxiety than children of heterosexual couples. They explained that children of straight couples feel more pressure to fit into their gender roles, and children of lesbian couples felt they had more freedom and choice. Interestingly, children of lesbian couples still fit into their gender role as they grew up: little girls loved pink, little boys loved blue, etc (because it is natural for us to match our peers to fit in, survival of the fittest and all) but as they got older they felt that they had more freedom in their life choices.
I'd have to say I think that's a great thing.
I think it is not so much that the children had two female parents, but rather (as this study states and other studies have shown) that lesbian couples tend to be very egalitarian. They share labor, whereas most straight couples tend to divide it based on gender (man works, woman cooks and does the dishes). I think it may also be a factor that lesbian couples would probably be more accepting of their children if they did stray from 'the norm', which puts less pressure on the kids.
So I guess straight couples need to learn how to share, and pull the sticks out of their asses.