A few issues but excellent.

This game rocks. The only thing I wish was that it was a direct port, not removing the sound test and ability to activate cheats.
Additionally, I have three main gripes:
1) the special stage. I was used to the old version, and with the new perspective and graphical tweaks my abilities have been thrown off. Worst issue I have. I managed to beat it, but only with Knuckles so far.
2) during boss attack, I noticed a bugged spot at the side of the screen in the hill top zone part. If you have the misfortune to fall into the lava, you expect to lose your rings but otherwise survive if youre fast enough, right? Here, you can fall into the platforms side and its treated like a bottomless pit or crush thing. Its a big problem.
3) a minor irritation: Hidden Palace zone doesnt have its original intended music, which was on the cartridge. What it has is Mystic Caverns 2P music, which doesnt fit very good and irritates me. When playing such a historically momentous thing (first time ever aside from mods), you should have original intentions wholly there.

Josh Mercenary about Sonic The Hedgehog 2 Classic, v3.0.1