Whereas Foursquare lets you earn badges and become the mayor of places, Scvngr gives you challenges to complete which earn you points. There are four basic challenges everywhere: Check-in, Social Check-in (a phone-bbump with another user!), Say something and Snap a picture. Once completed, you can also create your own challenge, or complete another user's.
The challenges you create can require a text or image response, although it appears you don't have to validate whether someone's attempt is successful or not. You can connect via a Scvngr account or Facebook Connect, and see what challenges your friends have made or completed.
Scvngr could really come into it's own if enough users join up and get involved. User created challenges are like really fun personalized 'notes' you can leave anywhere. Places you visit all the time could become full of odd things to do, and competitions to have with friends.
Scvngr is a very interesting addition to the world of location based apps, and its gaming focus has the potential to be much more fun than established services.