Really surprised by the number of Sonic 3 multiplayer tunes that snuck into the game. (Pleasantly surprised, though! They're some of my favourites.) That's a pretty hilarious pairing, though!
The soundtrack as a whole is a bit of a mixed bag, but that's always the way when you're taking the all-remix approach. Inherently, every single song is going to set up a little contest in your brain between it and the original version. And sometimes, it's going to lose that contest. I mean, you'd probably think Modern Planet Wisp was amazing if it was the first version of that song you'd ever heard. But it's not! So it doesn't have the impact. It just triggers your inner nit-picker. (Well, it certainly triggers MINE.)
My favourites are the ones that dodge direct comparisons by shifting into radically different styles. LOVE the big band Casino Night, the HUB music, the string versions of the Sonic 3 menu and Door Into Summer, the rock-and-horns GHZ, the hyper synth-pop Escape from the City, the crazy dance Speed Highway, and the string-and-piano Rooftop Run. It's also always fun to hear the stuff from the classic era, like the Sonic 3 multiplayer tunes, fleshed out with modern instruments. The "regular" versions of modern era songs, on the other hand, don't really have anywhere to grow and don't make much of an impact.
All and all, I think it's pretty good for what it is. There's a few duds and a few "why bother" barely-changed tunes, but there's a lot of good stuff too. (At least in the game proper. Some of the unlockable tunes are just hastily updated replicas with new sound libraries and should probably have just been left alone.)
Can't really comment on the gameplay, though. I'm avoiding watching any of the footage folks are recording at home... I feel like I've probably spoiled enough of the game already!