It would be fine if the user has the ability to filter a related list. Some related lists has a huge amount of records, but only a certain group are interesting for the user. It would be sufficient if the administrator could at least define one field on the related list which is filterable by the user.
10/18/2012 Edited title from "Filterable related lists" to "Related lists filterable by user", to help disambiguate from the idea Intelligent Related Lists
, which is about admin-level related list filtering.