The sort code in the Yhc libraries is faster than GHC. In some cases its asymptotically better. Some benchmarks have shown a doubling in performance. I know why this is, but will need to make sure the code is as good as it can be, check all the benchmarks agree etc.

Original work by Ian: http://www.haskell.org/pipermail/glasgow-haskell-users/2002-May/003376.html

I will track this down and aim for a libraries proposal in a month or so.