A couple of new details can be found in a recent hands-on that The Sonic Stadium had not too long ago.
"Apparently many players didn’t get as far as unlocking all of the Dream Events which is a scenario Sega wish to avoid this time round. Speaking of Dream Events Sega have been working closely with Nintendo and have been granted much more freedom with them meaning more items will appear from Sonic and Mario’s world to be used in whatever bizarre races they have planned this time."
So it seems that they've acknowledged that some didn't stick with the original long enough to even unlock the Dream Events (lack of interest/motivation?) so to avoid that, they'll probably have them unlocked early on.
"During certain races you’re given the ability to ‘boost’ by tapping the A button on the Wii Remote. The animation is different for each character but is usually a throwback to the past. Sonic for example does a spindash while Tails lifts a few feet from the air and propels himself forwards with his twin tails. Mario on the other hand has a spinning move as last seen in Mario Galaxy and Luigi appears to shoot himself forwards out of an imaginary cannon as seen in Smash Bros. As well as looking good tactical boosting could shave a good few seconds off your time."
Well, that's cool. It sounds like they're incorporating animations for special attacks in the same vein as SEGA Superstars Tennis.
Read the full report with more Mario & Sonic details here >>