If you have your own website that allows creating subdomains, this is a great way to send and receive files that are either too large to send as email attachments, or which corporate email systems block for fear of viruses (like executable applications). An outbound file or an inbound grant (permission for someone to send a file to you) appears as a link in a TB message.
The announcement messages (of a file received or grant offered) are bare-bones, and sometimes can trigger an overly sensitive spam filter; unfortunately there's no way to customize them. But that's a minor quibble. It works well and reliably. The developer is very helpful with questions posted on the associated newsgroup.