This movie, while separate from the anime's plot, really delves into Inuyasha's, and some of Sesshomaru's, pasts, which I really loved, and it showed how these pasts made them who they are. That emotional aspect was done very well.
However, the beginning bit with the sword, while explained later, seemed a little convenient... Definitely a plot device to get the movie going, instead of seeming like a natural part of the movie.
I also felt like much of this movie was just fighting, fighting, fighting, hence why I gave it such a low score. I understand that there is a lot of action in the show, and thus there should be in a movie as well, but I got bored with all of the fighting, as I felt like they were just stalling to make the movie longer, instead of getting on with it.
I really loved the ending scene after the credits, though, and Rin was as adorable as ever.
Overall, the emotional aspects of the movie were great, but there was just too much time spent on pointless fighting for me to have really enjoyed it.