It works when scope is genuinely negotiable and you control the roadmap. That is why it fits product companies and bootstrapped teams so well: nobody has promised a specific feature set to a specific customer on a specific date.
It fails when scope is contractual. Enterprise commitments, regulatory deadlines and platform migrations do not let you ship two thirds of the thing. It also fails when leadership treats the appetite as a target rather than a boundary, which quietly recreates the deadline death march it was designed to prevent.
And it fails on adoption more often than on mechanics. Fried is candid that trying to turn a company 180 degrees usually does not work, because existing momentum is real. Companies that mandate Shape Up organization-wide on a Monday tend to abandon it within two cycles.
Where operators split. Fried's method rests on judgment: someone decides an appetite up front, and he defends intuition over data-heavy analysis on the grounds that people are fundamentally feeling creatures. Ray Dalio would push the opposite way, weighting that same call by who has a track record and can explain the cause and effect behind it. The split is real and it is about evidence density. Dalio's approach needs a history of comparable decisions. Fried is working in the space where that history does not exist and waiting for it costs more than being occasionally wrong.