I was also surprised by the length of the demo. It felt like 5 minutes. I hope the full game has a nice mix of action and puzzles like God of War I/II... I think that's why I liked those games so much.
To me this game is exactly what ninja gaiden sigma is... a hack and slash or as someone already put it a button masher.
Not my type of game at all, although I do have to say both Heavenly Swords and Ninja Gaiden's engines are great engines... too bad they were used in games I don't care to play.
I don't recommend anyone upgrade their firmwares to download and try this. Its a 996MB download (which for some reason both this and the RE5 trailer downloaded really fast for me, like probably less then 40 min) and it just doesn't wow me that much.