Automatic downloads and past purchases are automatically included as part of iCloud's free service. Like its name implies, the automatic downloads feature allows you to automatically download any new music, TV shows, apps, and books you've bought, regardless of the device you originally bought it on. Using past purchases, you can access older purchases from the iTunes, iBooks, or App Store apps through their Purchased menu, and redownload any of them for free. (This latter option has been available for everyone to try in beta since June.)

If you want even more, however, there's iTunes Match. For $25 a year, the service will give you access to every song you own across any device you use (up to ten of them). Itching for your iMac's classic rock collection on a cross-country drive? With iTunes Match, you can download and play as you pass through Kansas. If you have any non-iTunes Store content, the service will first attempt to match it with a 256kbps-quality iTunes file; if that song isn't available in the catalog, Match will upload it to the cloud so that you can still play it on your devices.

In its current (developer-only beta) form, iTunes Match is only available to those in the United States, and prohibits users with large libraries (more than 25,000 songs) from signing up (possibly due to space constraints); we'll have to wait and see if either changes when the service officially launches to the public.

When iCloud launches, it will replace Apple's former sync service, MobileMe, and depreciate several features--namely, iWeb publishing, Gallery, and iDisk, though they won't sail off into the sunset for good until June 30, 2012. Current users have had their service extended to that same date, and, come iCloud's launch, they'll be able to migrate their data to an iCloud account. (Apple has published for current MobileMe subscribers that have any additional questions.)