Incredibly good compared to many other Naruto games!
The story mode uses cutscene-style animation, instead of the first three games' character-card style. This has potential, but due to poor animation and system lag, the story becomes broken. Also, many of the fights, even at the beginning, are extremely difficult, and seem very fixed. However, if you can become good enough, this is easily passable.
There are many (40) characters, and a lot of stages. This game actually ADDED characters from its Japanese version equivalent! However, even though the graphics look the same, many events in the US version make the framerate drop down to around 10 (Naruto's ultimate, many characters on screen at once, etc.), which is completely unacceptable on a home console. This lag is nowhere to be seen in the JP version.
Despite these downsides, this game is very fun, and is even more fun with friends.