Slow, slow movie, I felt like the characters didn't matter. At the end of the movie, you're supposed to be cheering for the main characters, but I found that I didn't care. They seriously could have cut out 45 minutes of the movie, and you wouldn't have missed anything.
I believe in the (very) short story, Benjamin is born both physically and mentally old--while in the movie he is just physically old.
I also wonder at the historical accuracy of some moments. Wasn't there a scene with Ben and Tizzy(?) on a bus where they make faces at some white children? Wouldn't this scene have been well before the 1950s?