Not bad
Good game if you are a Tenchu fan. The AI in the game is a little bit crazy, and some of the enemies are pretty tough. All in all a nice ninja game though. Graphically it is beautiful, the music, sound effects, and visuals create a nice atmosphere too. The control system is a bit complicated at first but if you are familiar with Tenchu then you should be able to pick it pretty quickly.
Also be aware that unless you have a pretty good grasp of Japanese this game might be pretty hard to follow. I'd recommend waiting for an English release if you don't think you are up to it.

Real ninja action
Finally a game thats worth enough to call itself a Tenchu-killer!