I have. I chose my own encryption password, but in order to restore files, I had to enter the password into the Backblaze web site. Backblaze used it to decrypt my files on their server and assemble them into a zip file on their server. They then sent me email saying I could download the zip file.
Also the Mac metadata weren't restored properly: http://www.haystacksoftware.com/arq/backblaze-backup-bouncer...