Tecmo put out a release for it, but word now is that it's actually up already on the Japanese store. The US store might get it tonight given the US press release:
The download size is 983MB.
NINJA GAIDEN® SIGMA DEMO NOW AVAILBLE
The action-packed, definitive ninja game can now be downloaded from the PlayStation® Network
TORRANCE, Calif. April 26, 2007— Tecmo® announced today that the release of the highly anticipated Ninja Gaiden Sigma playable demo is available now on the PLAYSTATION® Network. Take control of Master Ninja Ryu Hayabusa as he slices his way through enemy ninjas with dual-katana blades, blasts away evil fiends using ninpo magic, and overcomes insurmountable obstacles with the use of wall-jumping, ninja techniques.
“The Ninja Gaiden Sigma demo is a great way for PLAYSTATION®3 owners to get a sneak peek at the Team NINJA masterpiece,†said Yoh Watanabe, Tecmo’s Marketing Manager. “For the first time ever, Ninja Gaiden will be playable exclusively on a PlayStation platform and we’re amazed at how incredible Sigma looks and feels. This is the must-have demo for the must-have game.â€
The demo will feature 1080p ninja action at 60fps, new weapons, new combos and secret unlockable ninja content. The Ninja Gaiden Sigma demo is now available only on the PLAYSTATION Network!
The download size is 983MB.