I've finally taken the time to play this game. When i got it i knew i hadn't the time nor the patience to play it. Now i do.
It's amaaazing! Really good. It's fun, it's quick, it's hard. The challenges are fine-tuned and very welcome, the fast paced action is awesome. I don't mean the action-oriented combat, as the game makes it more fun to stealth through everything and it rewards you for it.You constantly keep scanning the rooms for obstacles and objects you can use for your benefit.
The game is very well polished, amazing cartoon cutscenes and a cool voice-over.
It reminds me of Tenchu back from the old Playstation days. Oh and the ninja stuff is awesome too!

Highly reccomended! (if you have the patience and time it takes)