The main feature is that it respects your privacy, a good sign in these dayss that P2P is not very well seen by governments and is under suspicion. All downloads are not centralized and all connections done by the program are encrypted, that's the way it keeps your privacy safe.
Search and download all kind of files: audio, video, pictures, documents, software... and it offers a special controls for audio and video.
You can configure it, for example, you can limit the upload bandwidth or the download bandwidth because you don't want it to monopolize your Internet connection and block it. Change the connection port or allow remote access.
Finally, you can add contacts to a Friends list and share files with them directly.
If you are using Windows Vista you must install OneSwarm for Vista.