Just a short summary of my first impressions:
Stages are pretty good. Quite interesting and much better than TD,
Boss Danmaku has some interesting patterns and is pretty fun, but nothing spectacular (wow factor) like Imperishable Night. I'd really like for ZUN to make more of the flowery grand patterns that kind of ended after UFO. Hopefully the later bosses contain some.
Graphics are great, though the new resolution means my laptop isn't wide enough
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Character designs are quite nice. I especially like the 3rd boss.
Music is quite disappointing though. It's nice to hear some of the leitmotifs from earlier games but the melody just doesn't really capture the feel of the game of give it an immersive atmophere in my opinion. TD was better in this aspect for the demo portion. Hopefully ZUN is saving up his ideas for later, it would be quite a letdown if the music continued around this standard (or became slightly worse overall as in TD)
Being someone who loves the Point of Collection, I am loving the life/bomb/score system
Overall: It's a good game and has quite a lot of potential, but isn't really promising anything spectacular at the moment.
@Zengeku: I might be wrong but I think it was the other way around with the demo being harder to get lives in?
EDIT: For some reason it seemed to lag on my computer the second time playing, though this might just be my laptop