Apart from some star quality acting, especially from Cameron Diaz who I've otherwised not seen perform such an emotionally powerful role before. I found the movie overly depressing with little entertainment value. The premis is effectively about how much life sucks and how little you can do to stop it, great. I really want to sit through a couple of hours reminding me of that fact.
I much prefered the ending on the book, although I agree it probably wouldn't have translated as well. At least that ending gave the film purpose, and a story quality. I spent most of the film with a tear down my eye, as did my friends and pretty much everyone else in the cinema. Aside from being moved emotionally though I really didn't appreciate it as a film, and really wouldn't watch it again.