Late to the party, I got the game for cheap (for local prices standart), and the most surprising thing for me are the wisp powers, and the fact you can unlock new tracks for red coins, it adds a new layer of deepness in Sonic games, the game is visually stuning, but there is a certain abuse with play-itself segments, I've unlocked only 2 worlds, and they are great, and I agree with you guys, this evolution of the Sonic formula actually worked and should be implemented and expanded in future releases.
I'd wish they could implemented at least 1 classic Green Hill stage though, I miss the grass in my Colors.
Great game so far, buy it!