It seems like you've got the LB and RB icons switched. These are the ones I've got in my game, but it seems like the top one should be RB, and the bottom one LB, to match on the controllers.
I don't have a great image, but this one sorta show off the bumpers:
This is probably more of personal opinion than anything else, but it threw me off to see other people's ghosts immediately once I started. It felt less like I could take my time to learn and more like someone sitting beside me, showing how bad I was. Worse was that the ghosts moved so far ahead I couldn't learn from them anyway.
So I ended up turning off the ghosts but then I ran into another problem, where I didn't know how to play, or use any of the advanced techniques, so occasionally I had to turn the ghosts on and just watch them play through it. This has happened so far in the first level where you need to hook onto the edge below where you start the level, and just now on the first blue level. Both of these I didn't feel were taught organically. I don't know if it's possible but it would be cool to get a little warmup to these concepts before going big leagues, I dunno.
It would be nice to have maybe another sound effect for the water splashing, it sounds exactly the same each time (not sure if there's much dynamic variation or not though).
In terms of insta-kill spikes, it feels like they're more punishing than I'd expect. I'm definitely coddled by mainstream games but having the spikes have what seems to be 1:1 hitboxes seems very punishing. I think (but I'm not sure) that even games like Super Meat Boy have a little leeway where you can overlap the hitboxes just a bit before you die. In RoN it seems like if you even breathe on them you're dead.
But man does the game ever feel good to play otherwise. You've absolutely nailed the sense of speed and momentum. It's so fun how in control you feel moving around, and the subtle wind that plays as you approach max speed is great. Haven't figured out what triggers the spinning hooks but I'm having a good time.
It would be cool if there was a way to instantly recharge your boost, even if it killed all momentum and increased your speedrun time by whatever so it couldn't be used for speedrunning. Sucks to have to sit still for a second or two totally motionless while I wait for my boost to recharge. I understand it's needed so you can't boost forever but man does it ever slow down gameplay if you stop.
On Trempe, I didn't immediately realize that I had to go backwards and up to cross the water gap, so I thought the game's checkpoints were bugging out because I didn't realize they only showed in a specific order, and that I needed to go down and up (if that makes sense)