"Gradual typing" works as a sales pitch, but having had a go at that it, it's at best a way of getting the editor to give better autocompletion. It's only with strict mode on that I feel Typescript is really worth it.

The article also touches on Typescript-in-JSDoc, but that can get really ugly with complex types and there are a few things I just couldn't figure out how to do when I gave it a proper shot last year.