Ask HN: How in the world do you optimize iPhone app promotion?

For the past week or two I've been trying out different methods to promote an iPhone app (I'll probably post it in a "review my startup" thread pretty soon).

The HN mantra is measure, quantify, A/B test, optimize, etc. The problem is that I'm very limited in what data I can actually get.

To some extent I can measure how effective my site is (for example, how many people click the "Download" button). But as soon as they enter the Apple ecosystem, they're gone. I have no idea how many people view the app's store page. I have no idea where they're coming from (other than from my website). I have no idea what the conversion rates in the final stage ("download") are, for users from different sources. I have no idea how effective the app description is - or, if I change it, whether it helps or hurts conversion rates.

I can maybe try to do some IP matching between visits to the website and people who launch the app, but this is very limited - for one, it only applies to users who download the app through my website; for another, there's no guarantee the IP will be the same.

Any ideas? Most of the advice for iPhone app promotion tends to be "get blogs to talk about you", which is fine, but doesn't really help optimize the process. I've found surprisingly little quality information on this topic.

Incidentally, I think this would be a "problem worth solving" - I can't be the only iPhone developer feeling this pain.