Well, rehearsing has so far thwarted every obstacle in previous zones... found a way to completely skip over the pits in Chemical Plant Zone 2, and managed to stay topside for both Aquatic Ruin zones. I just now did a quick playthrough of Casino Night Zone 1, and while like other zones a single misstep would spell a do-over, I can also see a lot of parts where I just need to be aware of surroundings enough to line up a jump reliably. I've managed to hit the pair of red springs in the blind every time in Aquatic Ruin Zone 2, a fairly narrow window.
But yeah, it could be frustrating... gonna tax my piano practicing skills to the limit!

Can't wait to get the whole thing tightened up and then go play my sister-in-law's console copy without telling her I've been practicing. It will probably get some surprised looks.
I am seeing a bunch of videos on youtube that get a lot more speed out of Sonic's spindash than I typically do, so I'm probably doing it slightly wrong. Noticed the game tends to have a few points where the controls are very particular... for example, if you're moving very quickly to the right and you hit jump while holding right, your speed will die the second you jump. If you're not holding right, you get full momentum and can make some incredible jumps.