I have only worked with Haskell on a personal basis, trying to understand if purity has any actual advantages. I have yet to be persuaded about the need to have code be pure. I never had any issue reasoning about impure code, and I do not find that the impure style has actually benefited me in any way. My logic bugs still continue to appear in pure code.

What I really find annoying is when I have to update state. I always have to write tones of functions in order to re-synthesize the data after the smallest change, and the deeper the data model tree is the more functions are needed.

Did I ever have any benefit from using the IO monad or the state monad? I don't know..it seems to be the number of bugs between my non-IO code and my IO code is roughly the same.

Perhaps it shines on a collaborative level...I don't know, I never had the chance of writing Haskell code with other people.