Im against it.
Monkey see monkey do.
Children see, learn, imititate.
Do you really think a child will have a "choice" at "sexual orientation" if he/she has been raised by a same-sex couple? watching dad1/dad2 french kissing.. or mom1/mom2 ?
Perhaps if they were limited to adopting a child of the opposite sex, the "effect" might be different, but thats just a wild argument.