Sadly, video files are not on the list of accepted formats. Yet. And users can only upload three MP3s in a 24-hour period. However, other file types, from PSDs to RTFs, are accepted and up- and downloadable.
According to the above-linked FriendFeed blog post, "This has been an especially popular request from organizations and companies that collaborate using FriendFeed groups. We've certainly been using this feature internally and have found it extremely useful. We hope it'll help make you and your collaborators even more productive, and a little more attached to FriendFeed."
Users can click the posted links to download files. With MP3s specifically, an embedded media player appears in the post.
Users can also choose to post via email, sending files as attachments to firstname.lastname@example.org. Naturally, there's a file-size limit, as well, which we hit pretty quickly while trying to upload a large Photoshop file and were given a simple "Could not upload" error message in return.
There's no pause or cancel button on uploads, and there are no clear guidelines yet on exactly what the size upload limits are, either for single files or cumulative daily uploads. Another missing link is a possible expiration date on uploaded files. While these questions remain unanswered, the biggest question in our minds is why the implementation of this feature took so long in the first place.