1. A user-interface method of selecting and presenting a collection of content items in which the presentation is ordered at least in part based on learning the preferred microgenres of content of the user as contained in content items selected by the user, the method comprising: providing access to a content system including a set of content items organized by genre information that characterizes the content items, wherein the genre information is specified by the content system, and wherein the set of content items contains microgenre metadata further characterizing the content items; receiving incremental input entered by the user for incrementally identifying desired content items; in response to the incremental input entered by the user, presenting a subset of content items to the user; receiving actions from the user selecting content items from the subset; analyzing the microgenre metadata within the selected content items to learn the preferred microgenres of the user; analyzing the date, day, and time of the user selection actions and analyzing at least one of the genre information and microgenre metadata of the selected content items to learn a periodicity of user selections of similar content items, wherein similarity is determined by comparing the at least one of the genre information and microgenre metadata of the selected content item with a previously selected content item, and wherein the periodicity indicates the amount of time between user selections of similar content items relative to a reference point; and associating the learned periodicity with the at least one of the genre information and microgenre metadata of the similar content items; in response to receiving subsequent incremental input entered by the user, selecting and ranking a collection of content items, wherein content items containing microgenre metadata matching more learned microgenre preferences of the user relative to other microgenre preferences are ranked more highly than other content items of the collection containing microgenre metadata matching less learned microgenre preferences of the user relative to other microgenre preferences, and wherein the selecting and presenting the collection of content items is further based on promoting the relevance of those content items characterized by genre information or containing microgenre metadata associated with periodicities matching the date, day, and time of the subsequent incremental input; and presenting the ranked collection of content items on a display device in an order reflecting the ranking of the content items.