Finished the first world with 100% of the objectives done. It's pretty much what I expected from the little I've played. First world is safe in terms of design/ideas, but it's comfortable/familiar. Stages also don't wear out their welcome as they're nice, short and compact. I think that was one of the issues with Yoshi's Island DS, stages were overly long and needlessly challenging. I don't think games/platformers like this always have to be difficult/challenging (same reasons why I loved Kirby's Epic Yarn), so I'm perfectly fine with this being a chill/relaxed go-to adventure game. Getting a score of "100" (which I'm surprised they changed) is definitely where the challenge will be, despite not having to do it all in one go.
As far as the music goes, so far, from my experience with World 1, it's been fine. Nothing too grating (aside from the enemy spawn pipe rooms) and there's been a few tracks that have stood out (like the mid-fortress tune) and the general theme/track that plays throughout most of the levels (which I think is the tune that is in most trailers). I put on some decent headphones so I can hear all of its brilliance (or terribleness?) and there's some good stuff here! The main theme that plays throughout World 1 has got some good baselines and the instrumentation on 1-6 is great (cool harmonica usage, nice guitar, etc.). I'm liking it.