Everyone commenting seems to not know that its not a romantic movie, its about a guy who slowly gets"destroyed" by living in the past, which is something more and more common these days, the ending might seem"heartbreaking" but that wasn't the intent at all, these themes are common throughout Shinkai's work. Its in a sense representing the realities of life while being much nicer in a sense. I think I can easily relate to the main character, which was the point really. I think if the story would have ended in a less"sad" note it would have made the whole thing quite shallow. But these are all only my thoughts I suppose, and to answer the question, yes its worth a watch, but don't watch it expecting generic anime romance smile.
To be honest I didn't like it very much. It did kind of hit home a little bit; I've more or less lost contact with some of my friends from elementary school, but I thought the movie was pretty boring. I can certainly see how some people would like it, of course. The movie's just not for everyone. Worth the watch, I guess.