2-sided material allows the use of two completely different materials for the front side and the back side of a thin object (without a volume). This can be used to simulate sheets of paper, tree leaves or, like shown on this example, a set of playing cards. The Arion v3.0.0 page has been updated!
2-sided material on playing cards
Here are a couple more examples also using other cool new materials and procedurals that will be announced soon:
2-sided material 
