Sorry if this is very obvious; I couldn't find anything in the FAQ or searching.

On artwork pages, between the "Add to Favorites" and "Report Spam" buttons, is the "I'm Using This!" button, which you can toggle between "I'm not using this".

What does it do, apart from remember your choice? For example, favourites leads to badges and adds things to the Favorites tab in your profile pages, but I couldn't find anything else to do with "I'm Using This!".