Net_URL_Mapper makes it easy to map an URL to application logic.
The URL syntax is similar to what can be found in Ruby on Rails or Python Routes module. The API and the design are different and try to offer a more OO approach while making use of interesting PHP5 only features. The URL syntax and the possibilities it offers are also more advanced and elegant than what can be found in the Zend Framework Controller at the moment.
Net_URL_Mapper does not perform the dispatching so it can be used with your own dispatcher. This way, it is a lot more flexible and reusable, and consequently more compliant with PEAR objectives. Net_URL_Mapper objectives are to provide a simple, common and flexible way to build nice URLs for your web applications and then use the results to do something. Dealing with Net_URL_Mapper results is left as an excercise to the developers.