The more reachable thumb keys look very interesting! But I'm wondering that aren't there more keyboards like this? Are there any tradeoffs? I'm thinking of the Cantor, Piantor, Corne, etc.

I currently have a Cantor that I like very much. The inner thumb keys are somewhat annoying, but not complete deal breakers to me.

Have you enabled permissive hold?

Also, Achordion is highly configurable, and was the missing piece I needed to have enjoyeable home-row mods.