Ashton Kutcher and Natalie Portman have done a really good job on the movie, and I'm gradually inclined to think that this was the best pair for the movie. Mr. Kutcher's charm was felt throughout and was great to watch! Mrs. Portman, on the other hand, fit into the character quite well. The intense, passionate, and the touching phase in the second half was a great contrast to the casual, messed-up, immature phase of the first half. The movie finally ends on a great note where Portman can't resist Kutcher anymore and falls in love with him.
Finally, I think this is a very entertaining movie to watch.