The music that is used for Daphne sounds more like the music they use in those 50's outer space movies. It has become tiresome and annoying. I think they could have come with some other romantic but ethereal melody for the ghost of Daphne instead of "it came from outer space" music. 
Yes, yes! That "creature from outerspace" music has been bothering me for a long time now. It belongs in low budget scifi flick and not on Dark Shadows at all! Considering the usual excellence of the DS scoring, it is surprising that they would use something that doesn't evoke anything spooky and sounds pretty cheesy.
My take on this 1970 ghostly love/possession story is that it would have been a lot more compelling had they not dragged it out far too long. I agree that everyone is acting pretty loopy here, even crazier than usual, which for DS is saying a lot! I guess you can cast the blame on spirit possession for some of them, but the same can't be said for Barnabas and Julia who should be in full possession of their own wits so far. Why in heaven's name don't they get the h*ll out of their and take David and Hallie with them, kicking and screaming if need be?
It almost seems that the writer(s) didn't really know where they were going with this story, or that they were still deciding the signifance of Rose Cottage and Daphne's and Gerard's reasons for becoming evil ghosts. By the way, I don't think that Daphne's ghost is good at all as she is clearly helping Gerard in
planning David's and Hallie's demise and she almost stabbed Quentin to death.
As ghosts Gerard and Daphne are a bit too corporeal to be that scary, although there are times when lighting and expression (i.e. Gerard's scowl) are used to good effect. I found Quentin's ghost a lot more menacing. His appearance seemed somehow more unexpected and understated. Ghosts that appear and over and act more like evil live people are simply not that scary.
Anyway, I am looking forward to 1840!
