When you say I/O in Haskell is sub-optimal, are you referring to performance, or the fact that it can be cumbersome? I personally love that Haskell's type syst

When you say I/O in Haskell is sub-optimal, are you referring to performance, or the fact that it can be cumbersome? I personally love that Haskell's type system tells you whether a function has any side effects, which of course includes I/O.