This add-on is great for several reasons:
1. It makes from creating a new theme a very easy process, useful for theme creators starting from C5 default theme. Of course, the cloned theme still must be customized to one's needs but that is beyond the scope of this add-on.
2. The developer is an established one, supporting C5 ecosystem by putting dedication in his work. Also, is granted that any question will have it's answer.
3. It's free and it does what it says.
4. Self hosted Google fonts for the cloned theme.

I wanted to modify a few things in Elemental, but I'd rather package it up than adding overrides in the application folder. Elemental Cloner works well for this purpose. After cloning the theme I uninstalled the add-on and everything still works fine.

I have lost count of the number of times I have used Elemental Cloner to create a starting point for a new theme.
Sometimes it is just for minor adaptations of Elemental.
Other times it is a complete new Bootstrap based theme where a clone from Elemental is stripped down and built out until it matches a design that looks nothing like the original.