It's good, but this game still carries the flaws of earlier titles, namely that it's too easy to lose rings and feel like its not your fault and that it's at its best when they don't put enemies and obstacles in unfair places. Also the time limit can fuck off. No need for it.
Dude, what? Too easy to lose rings? It's one hit and you lose health, how is that different from any other 2D platformer? And if anything, enemy placement and overall difficulty is miles ahead Sonic CD, Sonic 2 and Sonic 1. What are you doing that 10 minutes Is not enough time to finish the level? That's more than enough time.