Personally, I don't think that detracts or adds anything to his character. It does fill in some of the gaps of certain things, but it by no means makes the character any less.
Unless, you're John Cloud of Time Magazine, who writes this incredibly stupid point:
Yes, except: Why couldn't he tell us himself? The Potter books add up to more than 800,000 words before Dumbledore dies in Harry Potter and the Half-Blood Prince, and yet Rowling couldn't spare two of those words—"I'm gay"—to help define a central character's emotional identity? We can only conclude that Dumbledore saw his homosexuality as shameful and inappropriate to mention among his colleagues and students. His silence suggests a lack of personal integrity that is completely out of character.
Here's the major problem with the who article:
J. K. Rawling wrote a very complex, very "grey shades" (in that the characters - not even Potter, not even Dumbledore) are purely "good" or "evil" - they are imperfect, flawed people who are sometimes selfish, sometimes heroic, and try to do the best they can and have to choose between "what is Right, and what is Easy".
Perhaps there were good reasons Dumbledore didn't state his sexuality. After all, it really didn't matter to the storyline. J. K. Rowling, already recognizing that her books were controversial in some circles, didn't want to give her critics more ammunition. Maybe because Dumbledore wouldn't ever burden others with his issues.
Maybe because Rowling was writing about other issues - of power, and politics, and when to obey authority and when to appeal to a higher set of laws - and gay pride didn't really fit into the story.
So for her to say things afterwards and give more shading to the characters for the fans that wouldn't have fit into the story, I have no problem with that. I don't think that Dumbledore makes gay people look any worse or creepy for having a close relationship with Harry or anything else.
Dumbledore's out of the closet. Good for him. Maybe if Rowling writes another series of books, maybe she'll go ahead and have "Martin Fuzzlepot and his boyfriend Frank Blankenship" show up at a ball. Maybe she won't. But that's up to her, and I don't see how it makes her characters any less because they turn out to have more complexity later than we knew at the time.