Well, I can only speak for myself, but I had similar feelings of excitement when I was diagnosed.
See, I've always had this long list of quirks that makes me different from everyone else.
Over the years, these traits [like not being able to write correctly, talking to much (but only to people I'm comfortable around), sensitivity to certain fabrics, no "appropriate" friendships, etc]
have been making my life increasingly difficult. Not so difficult that I've regreted life or anything: just difficult in the sense that I was often steered away from the roads traveled by all my other peers.
Finally, my dad was like "Hey [Pundit23], I just heard about this thing called Asperger's, and well, I think you've got it. It explains [all of the aforementioned list]."
And my reaction was like, "Dad, it's seven in the morning on a sunday." But then of course, when we were all more awake, he explained that if all my impeding quirks were caused by Asperger's, there were psychiatrists out there who knew methods of compensating for the skills I lack.
And then after I got the confirmation diagnosis, I started reading up on it... and since then, I've been doing a lot of self discovery. The AS books out there are certainly erronious to some degrees (as AS is a broad spectrum sort of thing, all traits dont apply to everyone, and the field is just starting to be explored), but on the whole they helped me to understand myself alot.
So, when I'm asked "if there was a cure, would you take it" I'd be like hell no. I still think I became the individual I wanted to be, and I only need to compensate for the mundane little things that society and I don't quite see eye-to-eye in (Like timed tests). And sure I wish I had a lot more fulfilling friendships with wholesome people who don't use and abuse me -- but hey, perhaps if I was normal, I'd be getting involved with bad people right about now. It's all cool, and now that I know that I won't just outgrow my quirks, I can start taking them as seriously as psychiatrists do.
As for "why am I so happy"? Well, I think I'd be pretty freaking miserable if I didn't have AS. Because then I'd still have this list of quirks, causing a ruckus in my life, without any explanation or overall gameplan, all alone without a society or this rare feeling of actually belonging which I'm experiencing now. Quite frankly, if I was negative for AS, and I were given neither sympathy nor helping hand out of the hole I am in, I think that hole would have been my grave.
But now that we've started shedding light on the real culprit, I think I'll stay on this weird planet a little longer, and see how it all plays out. I'm no longer the only one, and I know that others have made things work. 