It can act as a UPnP media server... I have a Buffalo LinkTheater which is able to play mp3 among other audio formats and also plays XViD and DivX movies.
When starting up the LinkTheater I get a list of available UPnP media servers on the network.... and the router is one of them!!! I can navigate through the folders on the router and can play the movies and audio directly from it as well.
So this is at least one thing that works very nice (and was one of the reasons for me to buy it).
..... now if only my player would understand WPA.