Bxd5 is main line as you alluded to. Though understanding the system is not the same as memorizing the lines. The Danish was my weapon of choice for many years and 've played a dozen games against strong opponents with the main line (all the way up to the Qd2 Bxd2+ Nxd2) and this is where my opponents freeze because the books say "Black has an endgame advantage" because of his queenside majority.
I've had fun with white here and there are even more traps for Black in a position as quiet as this! :)
Most beginners are encouraged to play the Danish Gambit, because it teaches so much about initiative. Who hasn't seen the following move order?
1. e4 e5 2. d4 exd4 3. c3 dxc3 4. Bc4 cxb2 5. Bxb2
I think that the advise to play this is good for learning, but this advice is incomplete. I think that it's far more important to remember ideas than move orders. Having an understanding of the ideas behind this gambit system (or any system) will help when your opponent strays from the book move orders. Instead of trying to remember move orders, ask yourself, "What am I trying to do?"
I think my opponent in this match failed to understand the ideas behind the Danish Gambit. I say this because anyone who understands the ideas behind this gambit would not have played 6. exd5. Perhaps he had never faced 5...d5, and just didn't know how to react. Nonetheless, an understanding of the system would have prevented him from closing his own light-squared bishop. Check out the match and tell me your thoughts: