I think that sort of nails it: the problem with errors as values is errors become part of the type signature and put under user control, and the user can't really be trusted with that power.

Even the simplest functions tend to have error states - i.e. floating point math can always wind up handing back NaN.

So where I end up is, the default assumption is every function is effectively of a type MightError(T)...so why even make us type this? Why not just assume it, assume the unwrap handling code, and so you basically wind up back at try-catch exception handling as a syntactic sugar for that whole system.