Here's an official trailer for Soulcalibur IV touting all the new stuff it has to offer. It's worth it just to see the customized character they made — because a guy with a purple afro carrying a cricket bat is definitely some next-level shit for a fighter.
They also discuss Hilda, the armored-up female knight, and some new gameplay elements, such as the "Soul gauge" that controls when a character will have his or her block broken, leading to hits that destroy their equipment, and enabling their opponent's finishing move. Online play and the aformentioned deep customization options are also mentioned.