I'm an indie developer on Android, just starting to make an iOS version of my first app. My app is very well polished (look here http://www.pillowfightgames.com/jargoneer/) but it's still insanely hard to do marketing-- probably because I have no idea what I'm doing yet. Although the overall quality level of many apps isn't very good, good quality is still not enough to ensure good sales. Marketing is key, I think. I hope.