Yeah it can be used as currency or converted back to dollars.
I mainly convert it back to dollars but iv bought quite a few things just with bit coins. (3DMark11, COD, Dirt 3, other PC software)
Its not really worth your time anymore unless you have a efficient mining rig since 1bit coins only worth around $5 and it would of taken about 3-4 dollars to make it if your using something like a 6970.
Last year I got in and sold quite a lot at the right time (when it was worth $20 a bit coin made enough money to pay for my rig). Now Im just mainly doing it because it outputs the most heat and pays back the power bill.
Heat is good since my PC is in my fermenting room and its coming onto winter. So far its keeping my room between 26-30C where it would other wise be 10-19C