I really love being able to take the MBTI in my pocket. I speak in Myers-Briggs shorthand with a few of my friends, and this gives us another way to interact with one another.
I love the feature where you can place two personality types in contrast to learn how to communicate more effectively with people who may see the world from a different angle. I havent seen anything like this in the past.
My one critique is that the NT types and NF types get switched in a few of the deeper analysis parts of the app. This needs to be fixed in an update.
Segway To a Smackdown about Personality Types