"As an experiment, I temporarily pulled the Free app from the App Store over a month ago. Sales of the paid app remain great. Few complaints." What I like most about Arment and Instaper is he experiments with different monetization strategies for his app and API, and shares his thoughts and reasoning with the rest of the world.
I think sharing the stories, as we are all figuring this out is important for the industry as a whole, and it is great marketing. Arment says it's not just about the money, it's about the product. And he'll blog in detail about it soon.