Sure there is, you can play audio files of many many different types, far too many for me to remember and list here, play video files again of many different extensions.
DOn't have any music files on your PC?, fine use it to play your audio CD's
You could use it to catalogue your music library into one handy dandy place, after all that's the prime function of the Media Library
You could use it to manage your portable devices with the new plugins.
Or how about using it to rip your fave CD's to your PC so you can do any of the above things with them
Rip to mp3, ogg, acc etc etc
Or you could use it to burn CD's as well if that's your thing
Into podcasts?, SHOUTcast Wire for you then
And if all that isn't enough and you are feeling creative you could even try skinning the player or making some trippy visualisations for it to entertain others.
Or even set up your own radio station and use winamp to stream to others, you might not get many listeners at first, but there again who knows with the new and improved library there would be more chance of your stream being seen and not buried under the same old same old top 500
See, there are many many many different things you can do with winamp apart from listen to streaming audio/video, don't tell us you didn't realise?