I just wanted to add my experience. I found that Serana might be a source for a lot of the lag I get. The lag I see is almost always in combat with Serana, when she is using lightning or ice destruction spells. I also think her summoning a thrall causes memory probelms or lag.

In general, as soon as I could get rid of Serana, I did and haven't had any lag problems since.

The werewolf resistance to disease is bugged in Dawnguard. I contracted Rattles while a werewolf.

I had this happen for a different disease in skyrim vanilla as a werewolf. Only one time though, may just be a vary rare random glitch. Or can you catch a disease everytime?

Only had this happen once since I was a werewolf. Didn't notice it at first until everyone started asking me if I felt well?

I think it has happened in the past in vanilla as well, but was very rare. It seems that it is more common now, however.

For some reason when Serana is with me and I transform into the Vamp Lord, my vampiric drain bomb thing does like stupidly low damage... These needs to seriously be fixed cause I don't want to have to dismiss her just to use a simple skill :S. If someone has found a solution other than fully dismissing her then please let me know.

I've seriously got one very strange bug/glitch. Yesterday I finally finished the entire Dawnguard DLC, but I noticed that the "Awakening" achievement for some reason has disappeared. It basically no longer shows up as unlocked. Anyone else have a similar problem? [Xbox 360]

I also have the invisible shields, and i get the 2 sets of ripples when on water also when in VL form and roaming around the tundra ppl still stop and talk to me and give me quests instead of running in fear... I guess i'm not that scary