I'm pretty pessemistic from what we've seen. The modern clips haven't shown anything interesting (though admittedly the actual platforming is less marketable then early level fast-going) and the classic clips look plain wrong. I can almost physically feel the parts where Sonic loses all momentum at random moments, like every time he hits a spring or about half the time when he bounces off an enemy.
Considering a few parts of OC style gameplay resemble some of boom's gameplay, I also wonder if it wasn't originally planned to be that.
I'm looking forward to Mania though.
I'll agree about Modern's gameplay, they actively chose nothing of interest which quickly raised my eyebrows on this game's progress.
But Classic's gameplay actually seemed better than I was expecting. The level design doesn't seem quite as lavish or layered as Generations as of yet, but the acceleration and top speed made it look really fluid in motion and give it a better sense of flow and control than Gens I feel.
As for the momentum, I can't speak yet on the springs (especially since the majority of them in the trailer were hidden against a wall) but I think the momentum thing when hitting enemies was most likely the player's input. It's still weird if you instantly lose all momentum by letting go of the controller, but there are an equal amount of moments in the video where they bounce on an enemy chain pretty organically. I remember in the trailer thread some people were turned off at how Sonic seemed to plow through some enemies, despite different reactions from different jump heights being a thing since...
the first Green Hill lol.
Though it's not all entirely kosher for me yet. The stage having things like speed boosters for loops/auto-sections, bottomless pits, and the end-stage insta-death gimmick seem really reminiscent of Dimps, so despite me thinking it should control better than Generations/Lost World I'll hold my breath. Also I'm not sure what's up with
this moment of lost momentum after a tube, it's seems really similar to the "don't hold forward" programming tick of Mega Drive games.