Hm, gotta say, I'm not a huge fan of the new design. From a purely visual standpoint it looks decent I guess, but the way it's shaded just doesn't really click with me. I do like the new boots and the fact that Miku now has hair, but other than that this just looks... generic I guess. It looks like a fan redesign for Miku V2 to me, if that makes sense. Also, the artstyle (no hate to the artist, just a note) looks very similar to a lot of AI generated "art", and I feel like that's going to cause some discourse on the hellsite known as Twitter. It's a perfectly acceptable design, just not exactly my cup of tea.
EDIT: Just listened to the demo (yt wasn't working for me for a bit), and I think it sounds pretty good! Miku sounds at a happy medium between V3 and V4, with it being MILES better than V3 (most voicebanks are), and I feel just slightly fuzzier than V4. Pronunciation-wise, girl has never sounded better. As a sort of "test", on my first time through the song I looked away from the video to see if I could get any of the words on my own, and I actually got like half of them! This is a monumental improvement! Also just noticed, but her hair clip things are in the shape of a heart now. 0/10 give me my nice square hair clip things please (joke).