So far, so good: Learning Actionscript 3.0 really helped me a lot, now I'm finally understanding classes :D
It's really tough, but once you get the hang of it, it's really easy. But I didn't get the hang of it yet, it's slowly coming :)
Anyone who wants to start or migrate to AS3 better read this book.

Note: AS3's learning curve is steeper only if you dig yourself into a trench in AS2 (direct quote by a user), which is exactly what happened to me, but I'm slowly increasing my knowledge in it...;)