We've been using it for about a year in production across four projects and it's been a major boon for productivity because it allows our frontend developers to do simple backend features on their own. I think there are a lot of use cases where it would be a great fit for many projects and there are I'm sure a lot of companies that could save a lot of time by using it as part of their toolkit.
Also it doesn't have to be all or nothing. For example, there might be an API endpoint needed where there are multiple mutations needed inside a transaction but we just route between that custom backend and postgrest using nginx.
Other things we use:
- dbmate for migrations: https://github.com/amacneil/dbmate
- postgrest-client, a library I developed for constructing type-safe queries to Postgrest in Elm: https://github.com/alex-tan/postgrest-client