The "transformed" part of the title refers to a new mechanic in the game, which allows the racers to temporarily transform their cars into boats and planes at certain points in each stage. As you might expect, the handling of the cars drastically changes with the environment.
Many characters from the previous game are making their returns such as Ai Ai and Knuckles, but new racers include Skies of Arcadia's Vyse and likely several other unannounced faces.
Other new additions include an enhanced online mode, battle arenas, and even a new weapon system that allows you to block or dodge incoming attacks from your fellow racers.
See the trailer below to get a sense of the action:
The game will be available on multiple platforms, which currently includes PS3, PS Vita, 3DS, Xbox 360, and PC. We quite enjoyed the last game on the iPad, so here's hoping this one is as good or better. Expect to go racing with Sonic and friends at some point later this year.