I would like to start out by saying that this addon is like, stupidly impressive with the amount of unique sprites that have been made for all 8 directions which none look out of place stylistically with the OG sprites. The physics changes for the most part feel absolutely in line with the original S3, and make him much more fun than if it was just a reskinned vanilla Sonic with the Instashield and without the Thok. There's some parts of his gameplay I'd like to see some changes to, though.
First of all, the Spindash in the first two versions was WAY too weak if you were mashing, but in the current version (v1.2), I feel like its initial speed without mashing is TOO fast and is inconsistent with how vanilla chars' spindash speeds ramp up.
Small personal issue, but the Instashield hitbox feels juuuuust a smidge smaller than I expect.
Launching from springs and coming up out of water straight up just doesn't work sometimes. (See the red springs at the end of Deep Sea 3)
Final thing, trying to spindash on certain slopes straight up doesn't work, which I've experienced as a major problem on OLDC 2023 R1's Blossom Breeze 1, which the majority of slopes there have that problem. It doesn't happen in any vanilla maps as far as I know, but it's most likely a prominent issue on other custom maps, so I hope that's looked into for future versions.