Xbox Market Place has the KOF XIII demo up. I think the PS3 demo is coming next week.
For those with the game already, you can pick up EX Iori for $5 or unlock Saiki and Billy Kane for $1. Outside of Asia, EX Iori is DLC only and cannot be unlocked. Saiki and Billy can be unlocked in-game without paying.
Unlocking Billy and Sailki (the free way)
In order to use the console exclusive characters Billy Kane and Saiki, you must meet a certain number of TAs (Target Combos) before reaching Stage 4 in Arcade mode. Note: earning TAs only count if you defeated your opponent so fallen team members' TAs don't carry over.
Saiki - Preform at least 5 target actions per match in arcade mode. Saiki should then appear as a challenger, defeating him will unlock him
Billy Kane - Preform at least 2 target actions per match in arcade mode. He should then appear as a challenger, defeating him will unlock him