Well, I had a fairly long break from Skyrim. I was seriously disenchanted by the vanilla experience. I found it to be shallow, poorly written and the story poorly told.

Dawnguard has how ever to some extent made up for the original short fall. I've found the story (so far) to be engaging and the characters interesting. There has been a couple little things that have left me wondering what the developers were thinking when implementing some facets but nothing on the scale of Parthurnax and the Blades...
That atmosphere is quite well developed and story progression is fluid. I don't feel rushed, but I am still inclined to chase the story where as the MQ just really had no over bearing reason to be completed or for me to care about it.

Over all, I'd personally give the expansion an 8/10 (Skyrim would get a 5/10 from me).

In closing, good show Bethesda. Need more along the lines of Dawnguard.

Agreed. Dawnguard made me want to play this game more. Unforunately the Vanilla experience wasn't so emersive as this one was. Hope to see bigger dlc's that make me want to play so much as Dawnguard

I hope we get some extension or continuation of the main questline, or it goes down in my books as one of the biggest story telling failures.