I really don't get some of the complaints
"He isn't fast enough"
Well, if you have actually played the old games you should know that they were about action and precise platforming and exploration first and speed second, and that Sonic takes some time to accelerate and won't go top speed unless he's rolling down a slope.
"Sega should do something groundbreaking"
The result of Sega doing something groundbreaking with Sonic was adding lots of characters, transitioning to 3D and fucking up the gameplay, do you want that? It's better to go back to the basics.
"Mega man 9 style is the way to go"
No, new graphics is better than old graphics. The mega man 9 way would only be playing to peoples nostalgia and take away any chance to make new fans that the game has. If Nintendo could do a 'New' Super Mario Bros, then I expect Sega to be fully capable of making a 'New' Sonic.
The things that worries me are that the acceleration seems off and that the animations look slow and that the gravity seems too low. But we don't know what build of the game was shown. It transitioned directly to the level select, so it could be a beta or even an alpha build.
I LOVE ICELAND!