In my opinion, this is a valid alternative and not a straight deficit. Lua demands using a lot of maybe-nil values, and 90% of the usefulness of types still app

In my opinion, this is a valid alternative and not a straight deficit. Lua demands using a lot of maybe-nil values, and 90% of the usefulness of types still applies if you 'hide' this. And there is a productivity gain from not having to consider nils in your types, because handling often requires code, annotation, or thought. But there is a loss of productivity to fixing nil errors that aren't caught by other typing features. Places where the typing in Teal is still helpful: accessing the wrong thing, typos of variable names, wrong number or type of arguments to functions. That covers most of the statically-detectable errors.