1) I think Dumbledore being gay is so awesome! I've heard some gay people say, "Oh, but he didn't act gay enough or wasn't prominent enough to do anything for gay rights", etc, but I think they are missing the point entirely! This just goes to show anyone you know and respect could be gay, and it really shouldn't affect your opinion of that person. I believe, in movies, having a flamboyant gay character as the norm is actually starting to hurt gay rights. It's beginning to caricaturize gay people as a whole. Just like other types of people, there are many different types of gay people. I have three middle aged/old professors who are openly gay and it would be ridiculous to suggest that because they don't dress trendy, have the latest style hair or "talk gay", that they are failing to advance gay rights or something. Besides, someone's sexuality has NOTHING to do with the general storyline of the books and shouldn't be brought up anyway.
2) I hated how people started saying afterwards that Dumbledore was probably actually some creepy old pedophile who was gunning for Tom Riddle and Harry Potter. Gay old men are, as a majority, not pedophiles. It's such a narrow minded view and it scares me to think how people immediately turned their opinions against him. I wonder what will happen when this happens in real life? For example, if a decorated hero, using perhaps Lt. Michael Murphy, who was recently awarded the Medal of Honor for being killed by enemy fire while attempting to save his team, was discovered to be gay, would this affect people's view of him? Probably. Should it? No.
3) Dumbledore being gay, while not really having anything to do with the story of the Harry Potter books, turns Dumbledore into more of a Tragic Hero than Harry. One could almost(?) argue now that Dumbledore was JKR's principal character, not Harry. While Harry has been criticized as being a static character, Dumbledore is a character who started off as a kind, famous, powerful and all knowing wizard and ended as a person who people realized was very human, with very human mistakes, and the very human ability to experience love and loss. Grindelwald is Dumbledore's hamartia, and while one could argue Dumbledore did not experience peripeteia in a pure sense of the term, definitely Dumbledore having to battle his best friend and lover brought about his anagnorisis (aka, him realizing that the ideas he had formulated with Grindelwald was defintely evil and that he had to stand against ideas and people who supported them. Dumbledore is most definitely the Tragic Hero of this story. And I love him.