Nintendo Power preview summary:

Nunchuk to move Sonic, A to Jump and flick of the Wiimote to attack, and Z to block
Sounds great!

Knuckles, Shadow and Blaze are bosses in the game, they are part of a round table, once you beat them they become your friend. Looks like they are playable as well, though this is optional.
Great to see that they're bosses. Moreso looking forward to Knuckles than Shadow and Blaze. Can't wait to take control of the red Echidna!

Each environment has about 6 to 9 missions.
Eh... wasn't a big fan of the mission based levels in Secret Rings. Ah well...

Looks like there is 3 fighting styles to choose from. Cavalier style = speed. Paladin style = Strength or Knight Style = a balance of both.
Really interesting. This fighting style intrigues me, as long as it doesn't get in the way of the core Sonic platforming.

You can get new skills, like in Secret rings.
As long as you dont have to upgrade to get decent control and speed, it's fine by me.

There also seems to be a multiplayer mode (Battle and Survivor Mode)
No harm for putting it in, as long as it doesn't get in the way of the Single player dev time.

"There are Solo Missions designed specifically for ranked online challenges"
That's pretty cool. Glad to see they're incorporating Wi-Fi for replayability.

NGamer Preview:

Double edges sword slows Sonic's attacks down (most definetly due to the fighting style they chose)
So fighting styles affect his speed... looks like I'm going with Cavalier style.

The camera sits behind Sonic most of the time, switching to a side-on view for certain combat and platforming sections - just like Unleashed.
Awesome. The more 2.5D the better!

The winding track-like stages are as much racing game as platform game - just like Unleashed.
This is great, the more evidence of classic Sonic platforming the better.

Other gameplay elements will see Sonic returning to completed acts to take part in a series of missions and earn more followers.
Missions after the inital act: Ehh...

Later levels are likely to introduce slightly different play styles. We've even seen one that places Sonic atop a horse-drawn carriage, giving him the opportunity to fend off an ambush from a bunch of nimble assassins.
That's cool. If they can add different elements that's fine, but not to the point of how much the Werehog was implemented.