Why the heck should I use AS3?

I’m starting to get ahead in AS2 programming, it flows nicely and doesn’t really have any quirks (that I’ve seen yet).

However, now that CS3 is out (which I have), I tried using AS3, and it has a really arcane method of (for example) setting up buttons. All variables seem to need to have a declared type, yada yada yada.

So my question is: Why is AS3 better (if indeed it is)?

p.s. Anyone who answers the question in that it is related to performance, please be as technical as possible. Thanks.