TechCrunch thinks it could be the killer app for Firefox.
AllPeers is a simple, persistent buddy list in the browser. Initially, interaction with those buddies will be limited to discovering and sharing files – If you choose to, you can share any file on your network with one or more of your friends. They will be able to see what files you choose to share (even getting an RSS feed of new files you include), and with a single click download it to their own hard drive.
AllPeers will work even when the sharer is offline – AllPeers is a bittorent client, and will allow files to be pulled from multiple sources. When downloading, the file may be grabbed partially or fully from others you have shared it with (or who shared it with you). So a user just clicks on a file, and waits for it to eventually download.