Well, as the one that kinda started the discussion that led to that debate with XBlade and Shinra on the last page, I think I should say something here...
(note, I didn't waste my time reading your posts very carefully, just glancing them through. Sorry, but aside from the first few posts, you went somewhere totally elsewhere...)
First off, I also think it was kinda shoehorned in. There were subtle hints toward it during the last two seasons, but very subtle. But I bet it's simply because the creators couldn't do better if they wanted to keep making it. Nickelodeon would have never in their life allowed them to make the main characters bisexuals in what is a "kids show" to the them... That series would have died right there, which is sad. But leaving that revelation to the last episode and to that last moment, Nickelodeon had no choice but to go with it as they wouldn't allow one of their most popular shows to go without a finale either.
Second, I liked it. Despite coming out of nowhere unless you could read the subtle hints, it was a great finale. The last scene was great, whether you see them as close friends or something more. It was especially great since the episode before it was awesome, one of the best in the series actually. Whatever you think about gays or bis, I don't see it ruining the episode or the entire show, it was still so watered down and despite what the creators say, you're free to see what you want! ...even if you are boring and can't see it. And as a whole, I don't think the series really lived up to Avatar:TLA, but it is still one of the best western animations I've seen.
Third, gays and bisexuals are already kinda common and (sadly, only) mostly accepted, whether the conservatives like it or not. I see no reason to leave these out even in a "kid show" as long as it's well written. I think it's especially stupid since watching anime, which has had gays and lesbians for quite some time, we can't even have a simple kiss without someone setting themselves on fire? (...I hope nobody actually did.) As far as I know, Sailor Moon for example had some yuri in it and that's aimed mainly for young girls...and it's ancient!
Goddamnit, now I'm the one going offtopic... The main point is, chill guys, chill. One way or another, this ain't that big of a deal.