Taken from the latest Nintendo power:

– water color/hand drawn graphical style
– 4 party members
– character specific abilities
– 11 party members total
– Characters known thus far: Sonic, Tails, Amy, Knuckles, Amy, Rouge, Shadow, Big the Cat
– Full stylus control
– split team at certain moments
– rings = money
– no random battles, enemies can be seen
– turn-based fighting. Make attack selections for all characters before the animations continue
– special attacks play out like Elite Beat Agents
– team attacks
– “Fatigue Points” instead of MP
– ability to choose which attributes you level up
– purchase/level special attacks
– Rough story breakdown: Sonic is on vacation from defeating Eggman 2 years ago. Gets a call from Tails that Knuckles has been kidnapped by a group called the Marauders, and that 6 chaos emeralds are missing. Eggman not the main villain. But Bioware wants to make him a creditable bad guy again. Something about a “twist” between Eggman and Sonic that goes back to the earlier games.
– 2 acts: Sonic-themed areas and darker worlds
– Remixed classic tunes
– “fully animated cut scenes”
– simple dialogue trees
– Side quests