Quick read and valuable feedback. No idea how they were featured on the App Store for EVERY release, that's pretty insane. Sounds like they couldn't get retention down, but had solid acquisition.
Obviously design was a high priority, as they said, even inter-office documents had a high standard.
I think when you have a designer leading the team, design becomes the most important thing. When you have a programmer leading the team, the code becomes the most important thing. When you have a business person leading the team, it's the metrics, etc, etc. in reality the customer is the most important thing.