I completed the Oni Demo today. Addicting, but I'm not sure I even liked it. Even by the time I finished the last scene, I didn't really feel comfortable with the moves the character was performing... and I hate using a keyboard for movement.
Unless you have a really really fast computer, don't bother. With my 400MHz PowerBook G3, the only way I could get adequate performance was to turn the detail, resolution and colour bit-depth to minimum. Even at that setting, the game looked great, but not close to as nice as on the 450MHz G4 Cube at CompuSmart.
Even after I updated the video drivers on my 600MHz PIII W2K box I couldn't get Oni to run on it. Typical.
Update: Oh darn. James found a way to get more levels into Oni. Not gonna do it. Wouldn't be prudent.