I had already watched the anime and love it, so I felt that I had to give the manga a try. And I am very lad I did. The story had the same basic premise as the anime, but beyond that the story was completely different. I was particularly happy with this because it made it worthwhile to read both the manga and the anime; had they been the same then we could get the story by watching/reading only one.
The story itself was very good, and it managed to keep my interest despite having seen the anime (and knowing the truth about some of the characters because of it). There were some elements that were hinted at but not really developed and I was also a little saddened by the end. But overall, truly a beautiful story. 9/10
I thought the art was very nicely done. It's hard to compare manga art o anime art (where color and computers are both readily at your disposal) but for a manga I felt the art was very good. 9/10
The main reason that I love this story so much is that I really love the characters. All four of the main characters (Takeru, Ryou, Hikari, and Akari) bring something interesting to the development of the story. The main upside for the manga version (as opposed to the anime) is that there is much more development of Ryou and Akari. It was nice to be able to see their relationship blossom. The main downside is that there was a certain depth to Hikari's character that didn't make it into the manga, which I felt did take away from her character a bit. But certainly not enough to make me lose interest in her character. 9/10
As I've said, I really enjoyed this manga, so for enjoyment it gets 10/10. :)
Overall, I think this was very worthwhile and I'm happy to have read the story. I hope that other people give it a chance and are able to feel the same way.