Anything that depends on natural order of search doesn't work. For instance, in shop module where browsing product catalog is broken or
any other module/custom functionality that allows users to reorder nodes in the workbench in order to put them one after another the way users want to display them and then runs the query is broken the same way.
The reason for switching to the default value (false) for respectDocumentOrder in jackrabbit config files was more of an attempt to improve query performance when a large number of unsorted items was returned. This is actually no longer needed, as we limit the result set to the number of items being displayed and the items are usually sorted anyway.