It's been a long time since I've been involved with transferring files to and from clients, but even five years or so ago I recall enabling IIS's WebDAV mode in preference to handling customer-support calls about getting FTP working. Of course, WebDAV is still a ball of horror, even if it's not as bad as FTP, so please let's all stick to SFTP from now on?
Indeed. It worked pretty well, actually - in the standard Windows Explorer 'mount network drive' dialog, you could type an HTTP URL and get an ordinary-looking Explorer window and drag files to and fro.