from:
http://www.apple.com/icloud/features/ Beta. Available now.
Your past purchases. Available on all your devices.
Now you can download music you’ve previously purchased to all your
devices. When you buy music from iTunes, iCloud stores your purchase
history. So you can see the music you’ve bought — no matter which
device you bought it on. You can access your purchase history from the
iTunes Store on your Mac, PC, iPhone, iPad, or iPod touch. And since
you already own that music, you can tap to download your songs or
albums to any of your devices.
Coming This Fall
iTunes Match
If you want all the benefits of iTunes in the Cloud for music you
haven’t purchased from iTunes, iTunes Match is the perfect solution.
It lets you store your entire collection, including music you’ve
ripped from CDs or purchased somewhere other than iTunes. For just
$24.99 a year.2
Here’s how it works: iTunes determines which songs in your collection
are available in the iTunes Store. Any music with a match is
automatically added to your iCloud library for you to listen to
anytime, on any device. Since there are more than 18 million songs in
the iTunes Store, most of your music is probably already in iCloud.
All you have to upload is what iTunes can’t match. Which is much
faster than starting from scratch. And all the music iTunes matches
plays back at 256-Kbps iTunes Plus quality — even if your original
copy was of lower quality.