I have, yes. From a team perspective, there's zero technical difference between TypeScript types and a combination of default args and type checker functions. The same ends are achieved, but in a far less kludgy way that's overt. In the event a type checker is missing, it can be added/documented quickly with zero time wasted on trying to answer "what's the TypeScript way to do this?"

Types aren't the difficult part, it's TypeScript that's difficult. The documentation is a nightmare and in my experience I saw "any" types being used far too often (which literally defeats the purpose of using TypeScript).