PowerPC users, like us, really wont be able to take advantage of iCloud.
Although, I noticed it worked a few times for me. I dowloaded an app on my iPad which ended up on both my iPod Touch and iTunes list. I haven't seen this do this, again, since though.
The ideas are that you can upload all of your music to the cloud (for a yearly fee) and have all that same music stream to all your different iDevice antime over WiFi.
Also, by uploading music to the cloud, you have the option of freeing up memory on your iDevices by eliminating or reducing the amount of music stored on an iDevice.
The same with any photos, movies or data that you use in one iApp that you may have on your other iDevices, as well.
If allowed, they will, automatically, download to all of your other iDevices.
The problems I have with this technology is the you need a constant WiFi signal or Wifi/3G/4G access to do all of this. I live in a rural area and even if I go to areas around me that are more populated and have the places I go to that I know have WiFi access, there are only very few locations I can get wireless access.I do not want or have to pay for 3G/4G access,so my options are limited.
The issues are that with limited wireless access, I really can't see uploading my entire iTunes library to the cloud and not have any music on my iDevices. There would be times when I could never access my music this way.
Other than having a backup in the cloud of all of your mobile data, for security, I don't see the real advantage, at least for me, right now, to use this.