Daniel Bigham posted a link to his experiences in a Slashdot question/article comment, titled, Secrets of App World Success.
He mentions some key strategies: Keep the design simple, keep the app simple (don't make it a swiss army knife of features), make things quickly, find a niche/need area (if making an app, not a game) and time your releases better (don't submit your app over the weekend when everyone else does too).
Have any of you followed a similar rubric, and met much much success? I have. I didn't follow the simplicity rule very well, but the quick development time rule and release timing were a big help in preventing Open Fire Gold for iPhone for being a complete flop. (We actually went a little bit above break-even).