Having just picked up the PC port of Sonic & All-Stars Racing Transformed, I'm a bit late to the party, but not unfashionably so. There is, after all, still the pending 3DS version of the rather wonderful kart racer, to say nothing of the iOS version. Sega has nailed down a release date: February 12 in North America and Feb. 8 in Europe.
Multi-cart and single-cart multiplayer support for up to eight people is in, as are StreetPass challenges. The line-up for 3DS contains 22 characters, which shouldn't come as much of a surprise given the exclusivity of some of the racers on other platforms. Really, I'd be more concerned with how the spectacular tracks -- one of the biggest draws, by far -- look when scaled down significantly due to hardware constraints.
While supplies last, All-Stars Racing Transformed will have a Bonus Edition available at no extra cost which includes Metal Sonic as a playable character, the Outrun Bay track, unspecified challenges and time trials, and stickers for your license.