YES, Nexus 7 to TV Miracast WORKS
Hello I have been able to play YouTube Videos to a TV using an Apple TV 2 box and Nexus 7 Tablet using 'AppleTV Airplay Media Player" (free app by ZappoTV) over a common WiFi network. It took a few trys to get it working, so don't give up.
1. Connect your Apple TV and Nexus to the same Wifi network. Make note of Apple TV "Name".
2. Install (free app) above to Nexus 7
3. Tap AppleTVMedia icon to start app and Register First or Login
4. Tap Devices (Across Bottom of Screen are: Browse, Now Playing, MyZappoTV, Devices and Help)
5. You should see the Name of Your Apple TV. Tap and it should appear in Currently Selected Apple TV Player
6. Tap Browse and Select YouTube from List of Items (Video Podcasts, Android Gallery, ShoutCast, Facebook, Flickr, Picasa, etc...)
7. In YouTube, Tap Search and Enter fffastfffrank and Tap Submit
8. A Mobile Nations Video should appear, so Tap it. That is this author's recording.
9. Tap on Your Apple TV Player "Name" as you noted in Step 1. Player on Nexus 7 simply plays on your Tablet.
10. It takes a few moments depending on your network speed for the Now Playing Screen to appear with controls.
11. The Name of the Youtube Video should appear above the Pause, Start, Stop Controls with the time indicator.
12. At times, I have had to jump around to get it going.
If you figure out better steps, let me know and I can edit this so there is ONLY ONE ITEM TO READ.
I was also able to show photos from the Gallery on the Nexus 7. Should be able to play music, but still trying to get it going.
If this helps you, please give a thumbs up.
Good Luck, Frank