Chemical Hearts is certainly not a feel-good movie, and there's no reason why it should be. Theme of the movie; we can move on after heartbreak, and one day we'll look back only to realize that we wouldn't have done anything different. We still would have had a relationship with that person we knew we might never see again. We still would have interviewed for that dream job we knew we'd never get.
Strong acting by Abrams and Reinhart both, particularly when you look at all of the plotless, hollow teenage "romance" flicks that people of this generation are prone to. The movie certainly moves faster than the book, but the book has pages upon pages of room more to develop a story, so that's just par for the course.