All the rumors of Sonic being in Super Smash Brothers Brawl are true, I've used him myself. He's strong, but his attacks are wild, he is very difficult to master. But unfortunately, he is the only playable character from his series that was put into that game. Shadow appears too, but he isn't a playable character. He is only a support character you can find in an item.
I was really hoping to find Tails as a playable character, he's always been my favorite. But he isn't available as a playable character, just a freakin trophy, and not a very detailed one either.
Also disapointing: Mewtwo and Roy have been removed from the game, the stages are very small and hard not to run off the edge of all stages when using Sonic, Capt. Falcon, Fox and Falco. Also: Getting back onto the field before falling to your death is nigh impossible, even with the UP-B combination. EVERY stage has an underside that is very easy to get trapped beneath, and when that happens, YOU ARE SCREWED.