This movie is either not Japanese enough or not Hollywood enough.
It is a beautiful movie but with very little plot and very little... poetry. It is somehow not profound enough to be a good Japanese movie. On the other hand, the effects are good but the sword fights are only average.
Keanu Reeves does a classic Matrix performance. It is not bad, it is just not any different than most of his other movies.
What I do like about it is the introduction and inclusion of traditional Japanese myths. The movie is based on a legend of 47 ronin and the tale includes a witch, a dragon etc. That part it done really well.
If you like Japanese samurai movie, this is not a good example but still worth the time.