I do understand that there are many bugs that have been uncovered. I wish there weren't, but with the size of the game, and then the added code of Dawnguard, isn't it a good probability that there will be bugs? I work as a Laboratory IS Manager, and even after we test new releases, when we go live, someone discovers some glitch that we never anticipated.
I was lucky enough to finish DG with no bugs that I could think of. So it is possible. (lvl 79 breton, playing as Dawnguard)
I thought the dlc was very well done. I am not looking for pulitzer prize winning writing, or 100% story cohesion. It is a game meant to entertain, and it has done very well at doing that for me.
Forums, I find are generally where you hear all the negatives. So - I'd like to hear some good news for a change.
Mind you - my first character I had to quit after 350 hours due to bugs. But I got over that and my new one is doing fine, and I expect will continue to do so.
The only bug I have is the Serana wait/dismiss bug that leaves her nonviable as a follower....
But overall, i give Bethesda a whole lot of credit - this has to be one heck of a nightmare in programming...