Beware spoilers for Thor: The Dark World after the first image.
Sif. Man, this character did not get enough to do. Jaimie Alexander is great in the role as the warrior, and I selfishly wish she would have had more scenes. The story didn't focus much on her and the Warriors Three though, and they didn't have a ton of screen time. She kicked ass in what we did see of her, and I like that we got a glimpse of her softer side. Her implied jealousy of Jane worked okay but was possibly a hair overplayed. Not by much though.
Additionally, for all we know, she could have been doing better until the battle of New York - that probably plastered Thor's face all over media and brought up buckets of sad feelings. Granted, even that was over a year ago.
Now that I've justified her having emotions, let's focus on her brain. She might not be able to jump into battle in the same way as Frigga and Sif, but she was strong enough to not be killed by the Aether and she saved Earth and all the realms with her intelligence. She had help from those around her, especially Selvig, but she ran the show and did so under pressure that those of us who haven't had to save the planet can't imagine.
As far as Natalie Portman's acting? The word meh summarizes my feeling on that subject.
Overall, not such a bad group. I'd call it forward progress. What did you think of the women in Thor?