I saw Stranger Than Fiction last night, and enjoyed it very much. It has the same reality-bending sensibilities as movies like Being John Malkovich, Adaptation, and Eternal Sunshine of the Spotless Mind. Unlike those movies, it is not a black comedy or a depressing tragedy. It is funny and touching, with some very sweet moments.
Will Ferrell has been criticized as underacting, but I think he did a great job infusing a nebbish with innocent charm. And of course, Dustin Hoffman makes his character fascinatingly watchable.