Played this this weekend and I had a surprisingly enjoyable time with it. The stylus control was fairly well executed, special actions like climbing ledges or performing special moves (sonic dashing, tails flying, etc) were performed by tapping context-sensitive buttons that would pop up. The combat had a lot of Paper Mario-esque different minigame actions attached to special moves, which took me a bit to figure out as the demo did not include the corresponding tutorials. Also got a good taste of the running away minigame, as the enemies around me were low level and usually tried to bolt. It featured all four party members running after the fleeing enemies, with me having to tap each character to leap hazards along the way. If I missed too many jumps, they got away. If I caught them, combat resumed and I got a free attack round.
I also got a chance to have a little dialogue with an NPC and tackle a simple puzzle that involved splitting up my party to depress four buttons and lower all four sections of a bridge. The Sega guy next to me promised more complex puzzles later on, a lot of dialogue and story in the game, and at least 15 hours of play. Overall, I was impressed, and suddenly this game is quite heavily on my radar. What I saw was simple, but it was good simple; a solid foundation. If the quality there scales later in the game, and Bioware has crafted a decent story to drive it all, then this could very well be for Sonic what Super Mario RPG was for, y'know, Mario. Now that I think about it, the stories seem to have some suspicious parallels...