Let me begin with a confession: I have not been able to stand Maggie Gyllenhaal as an actress for years. I'm not sure where I got turned off. Maybe Casa de los Babys. Maybe later, with Happy Endings. I definitely couldn't take her in SherryBaby, and by the time she showed up in The Dark Knight, I had decided she was the worst part of most movies in which she appears.
Basically I feel she tries too hard in really dramatic performances. I also think she's completely ill-fit for characters with power or demanding professions, such as Rachel Dawes in TDK. Yet I also didn't wholly believe her right for the flakier, manic-pixie-dream-girl type she plays in Stranger Than Fiction. Honestly, I had some hope for her after seeing her in World Trade Center, but maybe it was just that I find her to be a good crier. And more tolerable when she's not in the lead.
This was not always the case. My introduction to her was with John Waters' Cecil B. Demented. I despised the movie, but I developed a crush on this young actress playing the Satanist obsessed with avant-garde filmmaker Kenneth Anger. And I continued to think she was fine in small roles in Donnie Darko and Adaptation. So it was pretty upsetting after eight years for her to go from being the best thing in a movie I hated to the worst thing in a movie I loved.