This is a great comment outlining some of Haskell's strengths. Definitely, ADTs should exist in every language claiming their static type system as a feature.

Just one thing that stands out to me:

> "Anything can be anything or sometimes nil" is a hard pill to swallow once you've used Haskell.

In a language like Java yes, nearly every type is inhabited by null. In fairness, a similar problem exists in Haskell: every type is inhabited by "bottom" which is the computation that never terminates. This is a side effect of being lazy by default.