Doesn't work with theme's

I wanted to use this sandbox to test a new theme. Installation took a lot of time, while my site isn’t that big. Anyway after succesfull installation I’ve created a ‘sandbox’, and activated a theme while I was “in” the sandbox. It all looked like it worked well, but the changes were immediatly visible for visitors to my site (I was monitoring this in a different browser, not logged in to my admin panel).

So, it seems the plugin doesn’t function. Installation and removing it later on didn’t seem to harm the system. I’ve read some complain it messes up the database or their installation, I didn’t have that issue, but since it doesn’t work as promised (and I know: that’s probably a hard job to code correct) it get’s only 1 star rating from me.