I used them at my financial services software company. They've made it through to our client's test environments, but as they're a large financial company thing

I used them at my financial services software company. They've made it through to our client's test environments, but as they're a large financial company things move very slowly and they're not in production yet. We wanted to ensure our APIs were backwards compatible and we felt like the best way to ensure that would be by making them contract led. This also means that we can design our APIs and write the spec files and get feedback without having to implement anything. So our APIs are defined by the swagger spec files. The open API generator was perfect for this as it meant we could write our spec files, and then generate interfaces for our spring boot application based on the swagger spec files. Then to implement the API all we need to do is implement the interfaces that the open API generator generated for us. The generator is very flexible (the mustache files allow you to modify what gets generated) and the community - particularly wing328hk were very helpful. We submitted a number of pull requests with changes that helped make things a bit smoother for us, and require less custom configuration of the generator. The development community was very active and happy to provide feedback and accept our pull requests. All in all I would definitely recommend a contract led approach (and the open API generator) for developing RESTful APIs.