ha! didn't know this was not hunted yet. I've been using this app and yeah it has three killer features:

1. It really adopted the "card-game" like gamification. It's fun to explore the decks
2. I love the deck sharing features. I can make my own one, and also can see other users's decks.
3. It's really "tiny" -> doesn't have much things you actually need to "study"