The plot is unique. Of course the game takes some ideas and concepts of "Legend of Zelda", but it is to scratch. Moreover, this is not an error for me because I'm a big fan Zelda.
With Okami you feel really put into a mythic, Japanese world.
Now to gameplay. Yes, it is, as a few reviews already mentioned before me, to swing some practice necessary to the divine brush properly. One should not try to draw very accurate or beautiful. Speed is the key, not precision. Pattern recognition of the game is in fact very good and not fussy. For example, just the most quickly draw lines with the Z button on the Nunchuk. The circles to the blossoming of the trees must not be circular. Speed is more important here. The slower you paint, the more blurred is the polylines and pattern recognition do not know what you've drawn.
Conclusion: Who Adventures like or a Zelda Fan Must Buy Okami.