The interesting part is that not one but two third parties come to mess things up. Then it gets interesting. The middle part is hilarious, which give the movie most of its appeal. Near the end, it gets a bit dramatic, it gets more points there. However, it ends well, which is not such a bad thing, but I would have ripped the last scene out to make it much better. Hollywood likes to tie all the loose ends too much for its artistic good.
That being said, Katherine Heigl and James Marsden are excellent, very funny, and easy to relate to. She story, even if it doesn't bring anything new, is interesting, and the plot developments are not too bad, to the exception of the "unforgivable lie" which rears its ugly head again. How tiresome.
You want a nice romantic comedy with enjoyable characters, it's for you.
7*/10