Yes, it's legit
I discovered the functionality worked when I set up my Apple TV and iTunes. I configured Home Sharing and was able to stream anything from my library to the Apple TV. Surprisingly, the function works well. I expected an echo effect as I usually do with Bluetooth but didn't hear one. It's extremely nice and doesn't miss a beat! It allowed me to play music from the iMac (computer room) to the Apple TV (living room). Having the ability to control the volume on either unit from the iMac was nice.
I then tested the function with the iPhone Apple "Remote" app and gave the the same functionality. I'm not sure if I was given that option prior to this week's iTunes update. To ensure you have the option, I'd suggest updating your Mac OS and iTunes version. This feature works with iOS 4.1.
Keep in mind, you must enable Home Sharing, enable ALL remotes within iTunes to pair with iPod, iPad, & iPhone under the same iTunes account.
Lastly, if iTunes, Apple TV or the Remote app does not find either of your shared libraries, ensure that libraries are SHARED/ON and that your iOS devices are on the same wireless/wired network. All iOS devices and Mac/PC systems must be within or fall under the same IP range and subnet. You may have to setup port-forwarding or open certain ports. I can't recall the port numbers on your routers.
I can't think of anything else. Create DJ playlists. Anyone in your household with access to your library can be the DJ or request songs from their iOS device. Great for bars, parties, etc.
I can't wait for more Airplay compatible speakers to come out. I'll be first in line to grab a set for my basement, garage, and patio. So far, I'm very pleased. Music in every room at an affordable price and zero wires. Good luck!