I've been playing Sonic Mania even more. I was pretty unfair in my second sesh, I played through the second half of the game while tired off my nut but I've now done two further playthroughs as Knuckles and Tails. I plan to do a Knuckles & Knuckles playthrough next, and then hit some time trials.
First of all, the new levels. Studiopolis is good, and the second act of Mirage Saloon is one of the best acts in the game and the Knuckles act 1 is great. Press Garden act 1 is still a mess, I guess there's a printing press in the background but the theming is so weak! The shading in this level is awful, it all looks really amateur. The second act is better but I still don't love it. Titanic Monarch suffers from following up a superior metal themed zone, with poor shading, more linear level design and a dependency on trite gimmicks.
The music is entirely great. All of Tee Lopes' music is great and I love the opening cinematic music by Hyper Potions (and the animation by Tyson Hesse is incredibly on-point as far as replicating the appeal of the original Japanese artwork)
Obviously, Christian Whitehead's work recreating the original games' physics, visuals and feel is praiseworthy to an extreme. The extension of that work towards creating a Saturn-esque sequel is commendable. I love the primitive 3D that the game uses most notable in Stardust Speedway act 2 boss as you rise up the tower, and Robotnik at the top.
The remade levels are generally strong. I'm a big fan of Stardust Speedway. Metallic Madness was good and the second act music might be my favourite in the game.