Even though this movie had nothing to do with the main plot of the show (or even existing sideplots), I actually found it to be my favorite of the four. Many of the characters created for this were adorable, and I fell in love with them all, watching them as they grew in the hour and a half of this movie. I felt that they meshed very well with the main cast of Inuyasha.
I also loved the music, and felt that it matched the rest of the show's music very well. The humor was spot-on, and the action was good--not like the movie before, where the fighting went on so long that it was boring.
Overall, for a spin-off movie, it's pretty darn good.