Jan Nasiadka from scalac contacted me to get some feedback about our usage of ZIO. My answers below, since they can benefit the community more broadly.
Context: we use ZIO in the context of https://rudder.io, a scala application that is 11 years old - far from a greenfield application with ZIO as base architectural choice. We used ZIO as a better framework to cleanly manage errors, porting piece of existing code to it. We are part of ZIO community since 2018 (since ZIO inception, when it was not yet ZIO but a part of scalaz, and when there was only a bifunctor, no context in it). Given our usage, we use ZIO in a specific way: we have tons of entry points and evaluation of ZIO effects, not one main entry point in the "main" method of the app. For correctness, that forced us to call a lot of blocking effects (you never know what a java lib is doing), and so we stressed the thread pool ergonomics, and helped make that part better (and some part