It finally answered a 39 year old question. Why did the biggest, baddest weapon ever built have such a fatal flaw? One where a single fighter with a well placed shot could set off a chain reaction that would bring the whole thing down. Well, now we know. It was done on purpose. And makes a lot more sense that a disgruntled engineer that was designing the D.S. and a defecting Imperial pilot were the reason why the Rebels knew the weakness. Not just that they "found a weakness" as we were originally told.
Also, that scene where Vader steps out of the darkness and goes apeshit on a hallway full of rebels brought out the 10 year old kid that loved Star Wars in me again. Pure awesomeness by the greatest movie villain of all time.
One thing that bugs me though... In the original Star Wars, when the Death Star fired on Alderaan, the entire planet exploded immediately. In this movie, when it hit it only causes a massive explosion that generates outward. I realize it made for more excitement with the escape in the first one, and more drama with the impending doom for the heroes in the second, but I didn't like that difference.