Dawnguard looks great but I have a very good feeling I won't be satisfied as I was with the original storyline arc and even the side questing storylines. I probably will not be throwing my money into Bethesda anymore since I lack the trust in them to give me quality content.
I'd like to see the responses I get to convince myself that perhaps I'm wrong.
tldr; I don't think Dawnguard should be worth money after the initial cost, especially given the quality of the initial content before and after the patches.