It's Friday night so I'm hacking around on Acorn a little bit and I stumble upon a giant speed boost to shape layers because past Gus just assumed things on ARM worked the same on Intel, or at least didn't check up on some prior assumptions.

Anyway, shape layers are hella faster (~3x faster at drawing on my Mac) in the 8.4 betas: https://flyingmeat.com/download/latest/