Eye opening iPhone software statistics from Pinch Media with realistic sounding analysis: free vs paid, does advertizing pay off, counting eyeballs. Here's the slides.
It's always better to know what you're doing. The next best thing is to follow closely the reactions to your (random) actions. The worst thing is to just hope for the best. However on the average it's better to do something, than nothing at all. If you fail, then fail spectacularly.