A new version of the NXT library has been released, and it supports Windows!! I lamented a few weeks ago that it only ran on Unix/MacOs (requiring the unix package and using Posix file descriptors), but that's a thing of the past. It was really easy to port Mitar's code to use the serialport package instead of file descriptors. Now Mitar has merged back my changes, we've tested the code on Linux and Windows, and it's been released on Hackage!
So now I can control my Lego Mindstorm robot from Haskell on my Windows machine! World domination is only a couple more steps away!
I wish to point out that Mitar's code is extremely well commented and a pleasure to work with, which of course made the adaptation to Windows a lot easier. Thank you!