Monads are a class of hard drugs

I don't think the author groks monads or writing maintainable Haskell.

> The essence of monads is to use abstract types to enclose a mutable state

That's not really true. Many types that are monads are just data. Some trivial examples: List, Maybe, Either, Free. There are several other misunderstandings in the post.

> For one thing, when you use a monad, you get hooked to it: the type constructors of the monad start to appear in the signatures of your function.

Only if you write unmaintainable code. I wrote a full RFC 2616 HTTP server and basically every function lives inside a completely parameterized monad type `m`. All of the dependencies each function needs are injected as arguments (See http://www.haskellforall.com/2012/05/scrap-your-type-classes...).

Also these days (though not when the article was written in 2008), free monad DSLs are becoming a very popular way to abstract away this stuff (See http://degoes.net/articles/modern-fp)

wrt "darcs is slow": the darcs source repo is 59M and took 3:27 for me to clone. Git's repo is 117M and took 6:02 to clone. So per repo size they're pretty similar. Darcs has its issues, but under normal conditions it's not notably slower than git.

Writing a monad blog post is obligatory for all who know monads. Here's mine: a monad is a class with a sensible flatMap operation. Hope that helps you understand monads...

I suspect Haskell is a bit faster now than it was in early 2008.