The home page clearly explain what the software does, the signup process is really simple and straightforward, and it's free.
Once you get inside, you have a fake board which is there to help you get started.. It took me 2 minutes to try and understand how everything worked. No magic, no complicated features.. really simple and intuitive.
I love the "reverse of a card" concept, the small animations when you drag a card, how you can easily "add people" to cards, how an avatar is automatically generated for you (With your first letter and a small icon), and more importantly, how there're just a few well-done features instead of a thousand of useless and over complicated stuff.
Furthurmore, it seems that the app introduce the concept of plugins where anyone could potentially incorporate only the features they want.
Overall, 10/10, great app!