Having adopted three kids, I am in favor of gay couples adopting.
I have two personal experiences with gay parenthood.
One of my besties is a gay man who is the bio father of a little boy born to a lesbian couple. He is active in the family role - it's really amazing to see - and their child has to be the luckiest chap alive being raised by this group of people. The family is way more emotionally stable than most traditional families you see.
Also, another friend of mine had two children with her husband, then left him to be a lesbian, raising the children with her partner and keeping a surprisingly good relationship with the father. Today the kids are high functioning adults, quite accomplished, educated, secure, would make any parent proud.
I think as long as a child is loved and wanted, nurtured and cared for, the specifics of the family makeup aren't important. I'm not sure why non-traditional families piss so many people off considering the extremely poor parenting we see every day from hetero couples. Obviously it threatens them in some way.