Me either. On one hand, it's more api clutter. Once you add it, it never goes away. On the other hand, foldWithKey vs. foldlWithKey is just confusing. But if there was some sort of consensus that default is low to high, then I wouldn't mind so much. The unfortunate presence of both toList and toAscList seems to indicate a lack of consensus though (I think including both is silly too).
I conjecture that the logic, if any exists, behind having the two names is so that the Data.Map API can be applied to several implementations. And in another implementation it may be most efficient or most lazy to return elements in unsorted order. So there is a "toList" which asks for the easiest conversion to a list, and a "toAscList" which asks for the sorted version. As for this proposal, I vote to have toDescList and foldlWithKey. This would likely simplify one of my uses of Data.Map. -- Chris