I haven't read the manga, but tried to watch the anime, and I just couldn't. This neverending drama gave me an overdose of exagerated sentimentalism, and most characters were annoying as hell, especially Naho. The only thing I liked about the anime was the opening.
Fortunately, and this is rare enough to underline it, the live-action movie shines where the anime failed. What first strikes is the music. Despite the redundancy of the main theme and its variation during the whole movie, I thought that the soundtrack was beautiful and almost moved me to tears.
Secondly, I was highly surprised by the acting. I'm just blaming the writers who wanted to stick to the manga/anime characters a bit too much, which turns some emotional moments to almost auto-parody. But let's say that it just brings a smile in the middle of tears, for a final heartwarming sensation.
Some reviewers blame the scenes from the anime/manga that were missing in the movie. Well, the movie is 140min - long already, and I think it gets the true essence of the story. Actually, I think it's even better not to make it last too long, as the anime quickly got from "cute" to "unbearable" because of unnecessary lenghts. Plus, this is a teen drama, some concessions need to be done.
Visually, "Orange" impresses sometimes. Maybe too saturated at the end, with visible special effects, but overall they did a great job.