I tried the plugin on two of my sites: one is online, the other is under maintenance (basically I'm doing it from scratch). On the second the plugin did its job: it created the copy of the database and the site in a subfolder. For the first one, however, I have problems as it times out: probably the database and the site are too heavy for the settings I have. The good thing is that by running the plugin before any changes I can actually test the site without any problems.