I use a modified version of the importer plugin and changed the class name so it doesn't conflict. You can also make it look almost exactly like the demo by using use add_option() in the importer to import data into your options panel such as social icons, fonts, colours, settings and other things that the importer wouldn't usually do.
You can also use set_theme_mod() in the importer so it also sets the menu location, something the default importer doesn't do.
I might post an example if you guys are interested.
EDIT: Also 1Click demo installers can drastically cut down your support tickets. It is definitely something to look into.