I have created a few prototype web applications in small teams using the DTA design system for different government departments. The design system saved a lot of time in reducing the discussions around best practices, look and feel as other departments were generally aware of this design system. We were also able to save a lot of time in not having to build the components ourselves.
However, we encountered some difficulties with using the design system. Of the most critical were bug #896 (create-react-app doesn’t work out of the box) and bug #891 (can’t upgrade react-router). Other issues include not having a dirty state to the form controls and having to come up with out own typescript definitions (which I’d be happy to share).
I’d be happy to be contacted via email if you would like a more detailed view into how we use it in our different projects.