It looks like part of Apple’s iCloud is up and running now. I didn’t expect the ability to redownload music, apps and books to go live until iOS 5 is released sometime this fall. However, if you take a look at iTunes (I’m using it on a Mac), you’ll see a new “Purchased” link in the iTunes “Quick Links” right sidebar. Selecting it leads you to a iTunes section that lets you see ever song (including entire albums), app and book you have purchased through iTunes.
Items (songs, apps or books) that were purchased and on your computer are listed as “Downloaded.” Items that were purchased but not on your device have a little cloud icon with a down arrow in it. Tapping the cloud icon prompts you for your iTunes password and then proceeds to download the item which was previously purchased but not on the computer you are using.
The ability to download previously purchased iTunes content should be welcome by anyone who has, for example, lost a hard drive without proper backup and would like to redownload their iTunes library. This previously required a special request to Apple.