Italian Apple blog Ispazio pointed out [Google translation] an interesting new iTunes App Store feature late last week: pop-up windows that appear with a click, making most descriptive information available without having to reload a full page. This feature is available in the Mac and Windows versions of the App Store.
By hovering over an icon in the App Store, a small "info" icon appears, denoting that more information is available for viewing prior to purchasing an app. Clicking the "i" immediately displays a pop-up window with several tabs displaying a description of the app, the "What's New" information describing updates, and screenshots for iPhone and iPad if applicable.
The person perusing the information needs go no further than the pop-up to purchase the app, although they can click a "Go to this app" link if they wish to see a larger view of the particular features of an app.
The pop-ups are an easily-overlooked, but very useful new addition to the App Store. They also work with movies and TV shows, where a "play" icon replaces the "info" icon and the description includes a video preview. The movie and TV show play icons have been available for a while, but the app pop-ups are definitely new.