I think DS did fairly well with continuity.
I give Dark Shadows about a C-, and when I consider the glaring discrepancies between 1967 and 1795, and between 1970 and 1840, I think I'm being generous. On the whole, I'd say that Dark Shadows has enough continuity so that I don't give up on it in despair, but is sufficiently lacking in continuity so that I still find it interesting.
Joan Bennett cracks me up when she screams. It's quite funny because it almost seems as if she is a bit embarrassed too.
Bennett did Grade A screams in 1795, when[spoiler]Naomi saw Barnabas biting Millicent.[/spoiler]Maybe she just couldn't get worked up over little Alex Stevens having a bad hair day.
I liked Beth's line to Judith when they were talking in the drawing room: "Would you like some more tea?" Desperately trying to steer the conversation away from dangerous depths and towards polite chit-chat.
The closing credits showed (besides the afghan previously noted by Pansity, toted over from the Old House where it was last seen covering, and then not covering, Jamison) a light fixture with three lightbulbs on the floor, and I'm sure the lightbulbs were lit. Very strange.