Very enjoyable
I thought this movie as a whole was pretty unrealistic, but taking that aside, it's a very entertaining piece of cinema. I think the general consensus is that Miriam Hopkins steals the show, and she certainly does, there's a part around the middle where she isn't in it for like 20 minutes (when they're elaborating on Bette's new beau Gig Young and then focusing on Deirdre) and I surely was missing her.
The good thing about Hopkins' character is that she did not elevate it into a caricature despite the over-the-topness of some of her scenes. In fact she reminded me of a few people I know who could act the same if circumstances were in their favour for success, and that I felt was an awesome treat, because I sincerely was expecting her to cross the line of making her character unbelievable. But she never does, she restrained her character's wild idiosyncrasies right in the point.
Davis, on the other hand, I think she has the less interesting character, but she does a lot with it. It was strange for me to see her in such a restrained character, but she made Kit endearing to the point where one does want her to upstage Hopkins in the same evil way she always does throughout the film. Campy Millie-shaking aside, her confrontation scene is great, and I really liked their early scenes in the film.
The rest of the characters do nothing for me really and serve more as devices for the two stars to shine more than anything else, with Gig Young as the best of the three, I think he gives a fine performance out of his character. I've always found it weird that both he and John Loder's character are so similar physically, but I guess this was intentional, on the Red Cross scene where the character is introduced I was very confused.