Apple Insider has posted results of Pinch Media's App Store usage report, which goes into detail on things like free app usage and how price drops affect apps.
There are many interesting statistics revealed, but one that speaks out is 5% of apps downloaded aren't used past the first month of download. In addition to this, only 20% of users continue to use free applications past the first day of downloading. Greg Yardley, Chief Executive of Pinch Media, has also made a statement about free applications. He said that, "[snip] unless there's something inherent about the app that screams free, sell it"," because applications with advertising built in simply do not generate enough money for developers. On average, free applications would need to generate $8.75 CPM (cost per thousand, to advertisers), but currently they only make 50c to $2 CPM. Hardly the numbers they need, so it doesn't warrant the time taken to develop programs for the App Store.
These statistics don't speak very highly of the quality of content available on Apple's store, but that doesn't stop it from being successful and having other companies follow suit.