Nice but...
There were ALOT of faulty hit tests for my comp, the character would stop halfway up a ramp or hill (obviously where each sprite ended), also, the game seemed to make my comp run it extremely slow. I play for 5 minutes and I only spent 52 game seconds in that level...make a detail setting so I can actually play this (I went and played minumun res and 256 color, still ran like crap...damn my 250mghrtz comp).
Anyways, I did like it, but the emulated audio was terible, didn't sound anything like Sonic games (and trust me, I own nearly every sonic game for the Sega Genesis, every one except Sonic 3 and Sonic Pinball) and the music was OK.
CHAO CHEAT/GLITCH!!!:
Play as Cream and start a game (doesn't matter what kind). Once your in, right click and press play, do that 3 times. Then, press Rewind and find the start button (It's hidden behind a wall but you can see the mouse pointer change). Start up a new game with a charater who ISN'T Cream and they have a Chao imitating their every move floating above them like Cream's Chao. :)