Played the leak, outside of the aforementioned performance issues, it's just not a very fun game. Sonic sounds REALLY off, the open world feels incredibly lifeless and soulless, and is just a mishmash of random springs, platforms, and rails everywhere that feel completely out of place, and collectables are EVERYWHERE. That's not a good thing, as it means it's slow and tedious just walking from boring platform challenge to platform challenge every five steps to grab a random collectable. The story is barebones so far, and what few levels there are are just rehashed levels from other games (WOO nostalgia pandering) but in 40 second snippets.
And the soundtrack? Hoo boy, from what I've heard so far (and I'm still early on), there's absolutely nothing there. The one constant that you could rely upon for a Sonic game has finally been removed. It's just sooooo bland, your traditional open world extremely basic background noise. The level themes themselves are just these synth tracks, which don't sound terrible, but have nothing that makes them stand out. No memorable melodies like in the other games, I could not hum a single track from the game if I was held at gunpoint.And of course, obligatory fishing minigame.
The controls are also that weird slippiness that Sonic has had in the 3D boost games where he just doesn't feel 'right' to control when you're wandering around, including a complete inability to turn around during jumps which makes it so you can jump at a thing to the left of you, and Sonic will careen right and fall off the edge despite the fact that your stick wasn't pointing ANYWHERE to the right.
But probably still better than Forces, so 8/10.
Quick edit: I had originally intended to download and only play a few minutes of it, in the hopes that it was good, so I could purchase it on Steam and support the devs. I will no longer do that, and just finish the Switch version, I don't feel it's worth the 60 bucks. Maybe when it drops to like 20 I'd actually pay for it.