Tried this out on Firefox 23 (Aurora)... it printed a long string of silly error messages ("Making more coffee..." "wow you chose a BIG file!") without actually doing anything, then froze the browser. After restarting, on the second try Firefox crashed. Anyone else having trouble?
Sharefest works with WebRTC - dataChannels, currently there isn't interoperability of this api between Chrome and Firefox. This swarm was created with a chrome browser so firefox leechers can't join the swarm (yet).