See demos.htm . The garbage collector interferes with smooth performance. After Hugs and GHC are merged, this problem should not be noticeable. As of very recently, Fran works with GHC . Performance is much better.
Installation is somewhat painful, but that situation is improving.
If you're interested, see HowToGHC.txt . Well, there are a few missing pieces, related to GreenCard, so you'd better wait. Try examples of your own. Then try it out. You can, however run the examples individually as explained in the header comment.