Watched Stranger Than Fiction on DVD the other night and really enjoyed it. If you like films along the lines of Adaptation or Eternal Sunshine of the Spotless Mind or even Groundhog Day, it's definitely worth a rental.
If you don't know anything about the plot, keep it that way. Best go into it knowing only that it's a bit of a mind bender.
If you've already seen it, though, you might like to read an early version of Stranger Than Fiction's script.
And here's the story of an odd coincidence involving another script with the same basic plot.