Actually I would love to see usage patterns among the free apps. Do people download a lot of free apps and use them, download a lot but delete after a day, or do people just download 1-3 free apps relevant to their interests (usually a better weather app, AIM, and Facebook) and not really "browse" the full gamut of the App Store?

Because I would not be surprised to find that only 25% of iPod/iPhone actually use the App Store beyond the above simple apps.

There's a lot of data about this if you google a bit. One of them is this: http://www.pinchmedia.com/appstore-secrets/

It mentions that only 30% of the users use a free app after the first day, and more stuff like that.