Are you referring to the graphics or the gameplay? I was disappointed that the 3DS version is different to the 360/PS3 but the best part imo will be using classic Sonic which i think is quite similar on the 3DS to the other versions.
I'm referring to the fact that there's going to be different levels and the fact that both sonic sections are in 2D. Just not my cup of tea, plus I really wan't to play City Escape which is my favorite sonic level.