Have been wondering much the same thing about TVD. They did slow down at the beginning of this year - there were two or three episodes in there where they were building the whole Katherine/Mason bit that were less than stellar - those were the episodes where we spent long bits of time with Stefan and Elena mooning over each other, or Caroline mooning over Matt. (Great decision to develop Tyler over Matt - the actor is better.)

Regarding DVD's? I think that's true about some tv shows. I admittedly rushed through and enjoyed True Blood and Dexter better than some did watching the series live. And it was certainly true about Farscape - the DVD's make it easier to ignore the weaker episodes. (Heck I noticed that when I rewatched Buffy a few years ago...I skipped over the episodes I didn't like.)