I'm sold on Copy.com. The Linux client is solid and as easy to use as DropBox's, and they have a tool to migrate your files from Google Drive, DropBox and Box.com directly over the web.
I've got 50G on Box.com, but mounting my folder via a webdav connection is a pain in the neck, the connection is slow, and I have to use an external sync application (the venerable Unison).