I really like the opening sequence, it's unique and stylish IMO.
I'm starting to think that I'm going to have to check out Mystery Inc. I never watched it because I figured it was just more of the same, but now I keep hearing about how good it was.
As for BTB, I know at first I was annoyed that they aren't sticking to the regular villains and supporting characters, but as I think about it more I'm getting more curious to see these different characters. For a while now I've been wanting to learn more about the different aspects of the DC and Marvel characters' mythologies and this could be a good opportunity to see some new aspects of Batman's outside of the comics.