Well, Nana tells half the story, at least. If you've already watched the anime adaptation, you'll follow right along with the major plot points, and then notice the abrupt end to the movie that hadn't even begun to tell the entire story. Thankfully, ads for Nana 2 accompany this movie, so you know the story continues there. For the type of movie it is, however, it could really use a distinct ending, or at least a cliffhanger ending.
Since I have watched the anime, it's hard to pull myself back and see how it would feel if I had not. I was awestruck by how well the live actors matched their hand-drawn counterparts. At least I was until Shinichi showed up, looking like he was about to hit his 30's rather than his mid-teen years. But Nana and Hachi were great, from their fashion sense to their demeanors. Actually, Nana felt a little less endearing than she did in the anime, but she was also less annoying. Nana's band is also impressive, probably with the Yasu's shiny noggin standing out the most. There is a bit of overacting every now and then, but overall the characters are all unique and well matched.
As for major plot points, most things seem to match up with the movie and the anime. A few scenes, however, might draw criticism. One example is when Nana mentions the story of why she bought herself a lavish red-dress after her grandma died. In the movie, her reasoning sounds rather frivolous. In the anime, however, it sounds like it was a freeing or almost uplifting experience for her. It's a pretty big difference that fans will cringe over.
Special features are sparse, but interesting. The "Director & Cast" feature gives a bit of background story on the Japanese actors who portray the characters in Nana. The "Japanese Original Trailers" is pretty self-explanatory, but it features several different cuts of the trailers that were aired in theaters.
As for whether Nana is an enjoyable movie or not, I'd say it is enjoyable in certain parts. It matches up with the anime episodes so well that it seems you could almost overlay one over the other at times. But it seems no work was put into making it its own cohesive movie. It's just like watching the anime series with a bit of editing for time. If there is a major idea behind this movie, it is to show that Nana and Hachi become friends and learn to trust each other. Watching that journey in this lengthy movie format, however, isn't very interesting. It plods along and if the ultimate point it's trying to make is that two girls become friends, it's not something you'll want to watch again.
