Hi Chris,
thank you for your article. As a freelance Sprintmaster (and UI/UX Designer) I had the opportunity to facilitate numerous Design Sprints in a lot of different contexts, including small family-owned businesses, early-stage startups or multinational companies.
When I look back, none of these weeks of hard work have been a “failed Sprint”. As GV says: “You either win or you learn”.
In my opinion, the Design Sprint shouldn’t be mistaken with a way to speed-up the production phase. It shouldn’t replace agile, lean UX or whatever process is already in used.
The Design Sprint comes BEFORE the project. Its purpose is to answer the questions: “Should we build that app/service/functionality? “ “Why would anyone care about this product?” …
Therefore a “failed” Sprint can be a great chance: nobody wants to spend months building a bad product.

I agree with you that the business stakeholders can become overly excited in some cases, but again, I see it as a great chance: for the first time, I’ve seen the Business actually CARE about user feedbacks.
For years we have been looking for ways to “sell” User Centric Design approaches and early user tests, without success. I guess the Design Sprint is great a way to “package” these services. I also see the Design Sprint as a great way to educate the Business, Marketing, Developers (….) to UX and User-centric Design and make everyone collaborate.
See it as an “introduction” to digital product design.

As you said this is not an easy process. As any great recipe, there is always a way to screw it up if you are a bad cook or if you work in the wrong kitchen ;)