Introduced , Home Sharing allows you to--among other things--play media from one computer on your local network on a different computer. In iOS 4.3, that feature gets extended to iOS devices as well. Once you've set up Home Sharing on your iPhone, iPad, or iPod touch, you'll be able to toggle back and forth between playing media from your local device and from Home Sharing-enabled computers on your network.
Setup is easy, if a bit obscure. First, you'll need to enter your Apple ID in Settings -> iPod; after that, you can access shared media via some combination of the iPod, Music, and Videos apps, depending on which iOS device you're using. Accessing your shared libraries isn't always obvious, though. On the iPhone, you tap the More button in the iPod app's toolbar and then select the new Shared option. You'll see all the shared iTunes libraries on your network (as well as your iPhone itself). Once you've tapped the shared library, all of the media you see in the iPod app refers to the shared library, illustrated by a titlebar at the top that bears the name of the computer to which you're connected.
On the iPad, on the other hand, you'll need to tap the Library header in the top left of the iPod app to access the shared libraries. In the iPad's Videos app, a new Shared toolbar option appears at the top of the app which lets you browse shared libraries on your local network. The disparate interfaces unfortunately make accessing shared libraries very confusing. (For more on setting up Home Sharing on iOS devices, check out ).
Performance in streaming is very good: music and short videos start playing almost immediately. Longer videos (or HD ones) can take some time to buffer before they start playing back. Quality is very good in all cases, with music nearly indistinguishable in quality from that on the local device and the video clear and easily watchable. Playback was smooth, even with multiple devices streaming from the same library, and I was able to scrub around in HD videos without having to wait for lengthy rebuffering times. Among the few drawbacks, the Genius feature isn't available when you're accessing shared libraries and, since Home Sharing only supports content in your iTunes library, you can't stream photos stored on your computer.