Renowned icon and app designer Louie Mantia -- who's been a guest on our design show, Iterate, not once but twice -- has shared his thoughts on app icons and their importance in an article on mantia.me:
[While] you can focus on marketing needs, that is a one-time scenario for each person. Any individual will only buy your app once. One time. It’s important to recognize that optimizing for this one situation may hinder the needs of your everyday user.
I believe good app icons are most valuable for your customers, your everyday users, not first-time shoppers.
Mantia shows a lot of examples, and even some brilliantly redesign suggestions for industry titans. Check it out.