Problems aside, this goes a long way on its look, sound, and vibe alone, which are so good they basically defined a legendary company for a generation. It might be the least of the Genesis Sonics, but that aforementioned non-gameplay stuff is already locked in, and it's truly wonderful. Green Hill Zone in particular feels like a turning point, and it remains one of the most memorable and comfy platformer environments to this day.
The rest of the Sonic experience, though, is still very much in-development. Most importantly, they hadn't quite figured out what a Sonic level should be yet. You get whole zones that demand a more careful and deliberate pace devoid of the famous momentum, and, in short, they suck. If you've played the sequels, you'll be dying for moves, power-ups, level design, and characters from them pretty quickly (not to mention extra lives and continues, goddamn), but honestly, that's okay. This was a necessary step. It's perfectly playable, and worth doing so just to absorb that Sonic feel in its earliest and purest form.
The rest of the Sonic experience, though, is still very much in-development. Most importantly, they hadn't quite figured out what a Sonic level should be yet. You get whole zones that demand a more careful and deliberate pace devoid of the famous momentum, and, in short, they suck. If you've played the sequels, you'll be dying for moves, power-ups, level design, and characters from them pretty quickly (not to mention extra lives and continues, goddamn), but honestly, that's okay. This was a necessary step. It's perfectly playable, and worth doing so just to absorb that Sonic feel in its earliest and purest form.