I just saw this tonight. I don't read much anymore; I am a slow reader, and so I can get through many more stories by watching movies than reading books. Also, I can get through a movie in one sitting, whereas the only book I have ever managed to read in one sitting was The Hobbit, when I was young.
I had trouble deciding whether the director wanted me to feel that Frank, or April, was the "bad guy," or whether they were both the bad guy, or whether neither was the bad guy. At first, I felt that the movie might be subtle, but it turned out to not be as subtle as I had first assumed. There wasn't much meat to the characters. The brief scene portraying the origin of their relationship at the start of the film is a hint of how much character development really goes on in the film. I did think that the fight scene at the end was potent. In the end, the film and characters were not "rooted" enough in anything for my tastes. For example, there wasn't enough of Frank's job shown to justify his boredom with it. There wasn't enough of the marriage shown to justify April's actions. Too much was assumed. Don't get me wrong; I'm a big fan of starting in the middle of the story with quite a few assumptions, and I write stories that way myself, but the assumptions have to play themselves out in the characters and story and I just didn't feel that I could backtrack to extrapolate these assumptions.
I do think that Kate Winslet did an outstanding job of portraying a character in fear of ceasing to exist; fairly spot on...
Overall: solid, good film but not great.