I found that if you go away from those 'core' libraries, quality drops sharply. Giving just one example may be unfair, but I do it anyways: the readline bindings (haskeline) didn't build on OS X for 2 major releases straight.
Haskeline is not bindings to readline or editline, but pure haskell. It does use libiconv, which is a chamber of horrors on OS X, and the source of your problems. But if you were using ghci you were using haskeline, so it wasn't that it couldn't be built. It is an extremely high quality library -- surprisingly, or perhaps not surprisingly, considering that it was written by a mathematician.
Sorry, you are right, libiconv was the problem. Still doesn't change that it couldn't be built on OS X for a long while (0.5 to 0.6 as far as I remember, 0.7 fixed things).
No, I didn't use ghci. I just tried to install darcs among other things.
Haskeline is not bindings to readline or editline, but pure haskell. It does use libiconv, which is a chamber of horrors on OS X, and the source of your problems. But if you were using ghci you were using haskeline, so it wasn't that it couldn't be built. It is an extremely high quality library -- surprisingly, or perhaps not surprisingly, considering that it was written by a mathematician.