*WP-Clone would be a five-star application if it actually worked.* My experience is that it almost always quits halfway through the process with either a 'timed out' error or a 'dropped database connection' -type error.
This plug-in potentially is the perfect tool for cloning a website quickly for a backup or for making a copy for use on a development server. It worked the first couple times, but never reliably and not without repeated attempts (and often after fussing with a whole bunch of WP/php/Apache settings). It never works for me now.