One of the reasons why file transfers are a great attribute to hosted IM programs is the fact that they are secure and save time. It usually takes less time to upload and send a file through a secure IM window in a program like Brosix then to open up your email program or window, attach the document, type out the email address of the recipient, and then, finally, send the email. A lot of work for one little file transfer!
Depending on the size of the file, it may take some time to send, but during this time, you are still able to have a conversation with your co-worker or friend while the file is being uploaded and made available for him or her to transfer and save to their own computer. When I was working full-time in a marketing department, we did this a few times and it really did save a lot of time, especially since our work email had to go through a company server and was sometimes delayed by ten minutes or more. Additionally, even though this was corporate email, it still wasn’t completely secure. Having a secure IM client can really ease some of these fears.