For teens and grown-ups
I thought that this movie was a cute romantic comedy. I know several friends that brought their under 13 kids to see it, but I think that some of the content is inappropriate for those kids.
There are several references to casual sex, with a neighbor that strips down in the main characters bedroom and a reference to Reese Witherspoon having an affair with a married man (which turns out to be untrue).
The main male character drinks a lot to try and cope with the loss of his wife, but stops drinking as the movie continues.
Overall, I enjoyed the movie and realize it was tame compared to most PG-13 movies these days. However, I do feel that it deserves it's PG-13 rating and wouldn't be appropriate for kids under 13. Also, parents who are concerned about references to casual sex should probably watch it before letting their kids see it regardless of their age.