Not really useful when so many geolocated images are so random. I don't necessarily want to see people's selfies or food pictures if I'm trying to see pics from a certain location.
The value of spotsy, however, is that you get to see which local spots have the most instagram photos associated with it, which provides value in a different sort of way.
I can see the usefulness of the app in that regard, but not as a photo browsing app.