Summarizing, my suggestions are:
1. Implement an efficient version of "withItem" for lazy and strict versions of "Map" and "IntMap".
2. Change the order of parameters from "lambda -> key" to "key -> lambda". The "updateLookupWithKey" example implementation shows how this change can be benefitial.
3. Begin the deprecation process of the following functions: insertWith, insertWithKey, insertLookupWithKey, adjust, adjustWithKey, update, updateWithKey, updateLookupWithKey, alter.