Yeah its fine, just a diet version of Sonic 2 with slight screen crunch and great chiptune versions of Sonic & Knuckles music (Sky Sanctury during the true final boss lolwut).
I will say, despite using save states, the way the Emeralds are handled is really dumb. Uses the two act structure of Sonic 2, but the "big ring at the end of the stage" thing from Sonic 1. Can only get the ring in Ac t 1, extrapolate from there.