Just a few of my own (premature) thoughts, having gotten through the catacombs and embarking on the castle proper:
I'm enjoying the game. There's stuff about it I don't care for, but it's pretty well made, and is fairly Castlevania-ish. Though it plays more like Ori meets Meat Boy than an IGAvania, but that's OK: it can be its own thing, as long as that diversion doesn't piss me off; and so far the devs have done a pretty good job of keeping me entertained.
I'll say one thing: I've had more fun with the 7 or so hours I've spent with it than I ever did in the same amount of time playing Bloodstained: ROTN. While ROTN feels more in line with the GBA and DS games in some ways, it's always felt so incomplete and unenjoyable. At least Belmont's Curse has some pretty good game mechanics, even if the area designs themselves are a little iffy and don't have any kind of logic of being a proper place of dwelling for beasties and Drac. That was something IGA usually got right: making the Demon Castle and its surroundings feel habitable and reasonable. Maybe I'll see more of that kind of logic further in, probably not: all the spoilery things I've seen just show more an abundance of spinny blade death traps and silliness like that. Somewhat fun from a gameplay perspective but doesn't make a whole lot of sense otherwise.
My biggest gripe with the game is the music. It's not offensive or bad necessarily, but it just exists—it doesn't evoke any kind of emotion, and there's certainly no discernible melody. It's the complete antithesis to Castlevania music and its legacy, more so than games with otherwise brilliant scores like the N64 games. Every area's music sounds the same and it's the weakest part of the whole experience. The art direction is also a bit iffy, and sometimes it's damn hard to discern what's happening in the background and foreground, and ends up looking like a bunch of vomit that I almost have to look beyond just to see what's happening on screen. As with the music, it's not terrible, but it's nothing that stands out either.
The most fun I've had in the game so far was sequence-breaking into a gauntlet room that shouldn't have been accessible until obtaining a double-jump ability, but I spent an hour or so luring a bat to the vertical gap that I could whip onto and swing from. The gauntlet took several tries against some powerful enemies, but I got mad XP for doing so and leveled up ten or so levels but actually need the double-jump to collect the prize chest, lol.
I should continue playing the game this weekend, but right now my CV focus is more on that massive(ly expensive) LP box set, and I'm enjoying a lot of the new recordings therein.
Maybe with more experience under their belt, the Bloodstained 2 devs will whip up something truly remarkable, or more reminiscent of the IGAvanias.