There’s a post a ways back about studies of the fitness of lesbian/gay parents. One major study (discussed there) is by Professor Mark Regnerus. His study is being used by the state of Michigan to support its ban on same-sex marriage in a case that features dueling studies (and to some extent dueling methodologies.) If you’re interested there’s a useful twitterfeed covering his testimony. I will wait till this is over to say more, but wanted to pass that link along.
The most immediately striking thing to me is that of 3000 people studied only 2 were raised by same-sex couples. (Something under three hundred had parents who had at least one same-sex relationship.) I’m not sure how firm a basis that can give you for any conclusion about same-sex couples as parents.