So HSoB... oh boi...
Guess there's no longer a point to leave everything behind spoilers? Seriously if you want to play the game already, go for it, it's good, appearently extra stage is coming in spring.
tl;dr this is both one of the easiest and the hardest experiences you will have in a Touhou game. Easiest, because anyone can 1cc this game, even on Lunatic, heck I did it by accident. However it's mainly due to the system of this game. As some people already put it, the patterns themselves get pretty intense around stage 5-6. Stage 5 boss, actually has a lot of amazing and hard gimmicks (Boulders, sandstorm circles) that go unused unless you do Lunatic. Even on Lunatic there are two spells you just might never encounter (Mystia's and Nebet's LW and Horou's LW), alternate Stage 6 route gimmick and to top it all off, the game looks gorgeous, as Mino put it "it feels like I'm watching a movie"?.
However that still has few downsides. While pleasing at first time for many, on repeated playthrough the eye candy can become an eye sore for some and there's just so many things this game throws at you and honestly... not everything works. The best example of it are many many different sub shots this game has. 9 gems for 4 characters? Does that mean we have 36 different sub shots?! Nah, not really. Most people will just use ReimuRed or ReimuYellow, homing really helps in this game and so is increased damage. PurpleSakuya's pretty good and Marisa has a couple of good options, but Kaguya seems to only work with Green/Jade ... and she's not even that good with it. Orange got nerfed to bits, which is kind of a shame, Black is still there for a challenge and Cyan/Blue/White are just there (Horou cannot switch your gems if you use Black/White I guess, Orange spell doesn't even seem to use the colour change, I guess it was changed last minute after the orange nerf?).
However boosting/balancing other gems and Kaguya for the extra stage patch will probably resolve most of these issues. Other than that I don't really have any. I really genuinely like this game and I kind of want to play it more, even if it gets tiring often. The stage design is excellent, they even made stage 3 more interesting and I think bosses aren't too far off. I know there are people still iffy on Horou and her design (I do like the concept of stage 1 boss becoming a final boss just because she got OP artifacts and because she has a dumb, but wholesome plan) and I guess either Shiran or Set could've been better final bosses? But again, I feel like Horou being final boss was intentional for trolling and presumably trying something different for once. I'd still say Ranran is probably my favorite character and design? She just... idk feels iconic to me, while everyone else is colourful and deep, it still feels like I need to read their lore to fully appreciate them.
Music wise it's also excellent. Feels like a true comeback of Wanwan to me after RSS (Trifocuser's music had some great pieces, but it overall felt like snoozefest to me). I don't think they're all neccesarily eargasmic (?), but I did find some favorites. Like holy cow, "Sinful Rampage" has no business sounding this good. He also got much better guitar samples, though I seem to be alone at thinking that they really added a lot to the themes like the Stage 6 theme.
Again, it just feels like devs are trying to outdo themselves instead of progressing or evolving, which is good, but it makes me wonder when they're going to reach their limit.