At one point it seemed that an App Store was a crazy venture. Webapps seemed like the best route, but it sounds like it's been paying off.
The chart above shows data gathered by Asymco that shows Apps are quickly gaining on music, and may do so in about half the time.
A personal note, we do remember a time when people were reluctant to jump on the digital distribution movement with music. It sounds silly looking back, and we are sure there are still some who would rather have the physical copy. But now buying a song for a dollar is seen as common. We aren't sure how big of a barrier Apps had to overcome to become mainstream.