Don't listen to anyone else, read this first.
I agree, at first I did not like this and was kinda regreting it. But then I beat the hero story and unlocked a butt load of characters, levels, modes, boards, and a new story. One of which includes Shadow who doesn't use a board but runs with his hover shoes.
Multiplayer is fun, 2 player is great but 4 player would be better. (besides the fact the screens are small)
The new characters ballance out the series and I think this was a good turn for sonic team. Trust me, Sonic for Genisis was my first video game and my favorite game is SA2:B so you can say I'm a sonic fan. Defiently worth trying if you'rte a die hard sonic fan.
There are cons. The turning takes some skill and clearly you have to try again and again to obtain it. Once you get it and can land the tricks, take the short cuts, and go the fastest speed...all those trails were worth it. (plus, kicking your friends butt in multiplayer is a good advantage)
So check it out, definently worth 40 bucks for the fun of trying to see all the secret characters they have in store. If money's tight, wait for a price drop...seeing other people's reactions, I'm guessing that'll be soon. :)