It was not a huge crowd; oddly subdued, really. I'm sure many of us were wishing the film had been released before the November vote on proposition 8 in California. On my way out after the movie I heard the ticket-takers saying there had been just over 200 of us. Hardly a full house.
During the reception before the film I ate some snacks and found that I knew no one in the lobby, so I trusted my fannish radar and walked up to someone and struck up a conversation. The fellow did indeed turn out to be an SF fan, and we chatted amiably about our favorite authors for a while, then he asked me:
Before you read on: what is your answer?
I was a little stuck on that question. Trouble and Her Friends came to mind as the first one like that I read where I also met the author. But I don't remember noting it when I first read about a gay couple in SF. Possible because I grew up in Ann Arbor, where being gay wasn't considered particularly strange. Thinking back after the show, I remembered that Heinlein had a few gay (and even trans) characters, but I think probably the first books in which I saw gay characters really be partners was in Mercedes Lackey's Valdemar series. He mentioned Stars in My Pocket Like Grains of Sand, by Samuel Delany. I happen to be reading Delany's autobiographical The Motion of Light in Water right now, which we both agreed is an excellent book. Sad to say, it is also the first book by Delany that I've read (unless I read Nova when I was young, but I can't remember for certain), though I have of course read several of his short stories.
Anyway, I hope you will answer the question and also ask it of other people because I think it is an interesting question.