The latest issue of PSM (April 2007) has a nice 10-page preview (and a featured cover ) on Ninja Gaiden Sigma with their own hands on experience with the game.
* Unspecified amount of original content for Sigma
* EVERYTHING was redone for Sigma: backgrounds, enemies, characters, animations, textures, etc. * Game will make use of the SIXAXIS in one way by helping to power up Ninpo magic while casting it
* Sigma will be 19 Chapters long, 3 more Chapters than the previous 2 versions
* A lot of the new stuff is when you are going to be playing as Rachel
* Will run at a constant 60 FPS with full self-shadowing and in 720p
* 3 ways to play - off the disk, off a partial install, or off a full install (for those who plan to play for long periods and don't want to worry about loads times. They wanted to give the gamer a choice on the matter)
* New difficulty level above the previous ones
* Still talking to Sony about what the possibilites are for downloadable content
* Karma ranking system/online leaderboards will be intact * Karma ranking/leaderboards will be improved upon by letting you view the results for a player's run through for specific chapters and how many times they died, etc.