It would be interesting to see timing results of this implementation. Similarly, comparisons to other implementations/algorithms. I will have to fire up erlang when I get home this evening.
I am basically a broken record on this topic, but I do like sending more people to see the Dancing Links algorithms solving this (and other related problems, such as sudoku.)[1] The techniques in DLX cut the search space for the 8-queens down to just 1,048 board states. (For 13, the number of boards is up to 1,046,318)