I know it is only anecdotal, but I am going to go with my personal experiences with families headed by gay couples. There were two classmates, one being a friend and playmate, of my older dd when she was in elementary school, and a third family whose dd was my younger dd's best buddy in preschool. We continue to socialize with two of these families.
There is also a family with one parent being a colleague of dh who have grown children who are doing quite well in life (one of whom has become a public figure ).
I have a family member who is gay and she and her partner have one child, also doing just fine thankyouverymuch. We see them on a regular basis.
I also worked with a lesbian couple who were providing fostercare. Their regular caseworker was on maternity leave and I covered for her for a couple months. I only wish all the foster parents I worked with were as wonderful as they were, as foster parents that is.