I think it depends on how deep you want to delve. I personally use it for enhancing myself as a designer and a place to archive all inspiration I gather from various internet sources. For example I like to “pin” great sketches, have a board dedicated to patterns that I intend to use when I want to do an audio product. I also use it for home inspiration, right now I’m keen to keep my living expenses low as I like to live and work in large cities so have been following the “micro home” movement.
That is just me as a designer. I don’t generally look in to the trending pages but from what I can gather and I use my girlfriend as an example here the average Pinterest user likes to look at and archive their lifestyle enhancing “research” mainly exercise, home decoration and cooking.
Now this could be a way to design the next kitchen utensil that lets you decorate that cake as it looks in the pictures, or helps you complete that exercise routine but that begs the question of designers just producing more “stuff”. It’s an interesting topic to explore but you have to remember people are using Pinterest as a way to explore a life they want to lead, not the one they are actually living.