I've been using keystone to run a small coffee roasting operation. The underlying concept (primsa + graphql + custom crud hooks + ootb ui) makes it incredible easily to model and build businesses processes.

Only compliant is that the admin UI isn't that flexible or extendable. You eventually end up rewriting standard views entirely when you need to add additional features that ideally would have just been minor extensions (eg adding a custom action to a record page)