That's not a particularly great example though because 99 bottles of beer is not a particularly stateful computation. You could easily do it without state at all like this: https://gist.github.com/lgastako/2e7dfd6b1118bb408ff114a4be4...

On the other hand this blog post http://www.haskellforall.com/2013/05/program-imperatively-us... demonstrates how one of the bits of Haskell that some people find complex (lenses) can be used together with the state monad to provide an "imperative-like" experience that's even nicer than most imperative languages.