I just received my ATV3 yesterday & I am quite pleased with it. With my subscriptions to Hulu+, Netflix, & my OTA Antenna, I'm more than happy. I actually just cancelled my Tv/Phone subscription to Fios, & now paying strictly for Internet service for 39.99/mo from a different provider.
However, I tried to mirror a few kids apps such as Cartoon Network, Disney Junior, & PBS Kids with no luck. Same with other apps such as Comedy Central Stand Up, Showtime Anytime, & a few more.
I was under the impression that you can mirror ANYTHING to the ATV3 but this simply isn't the case. All these apps use their own media player that's built into the app that doesn't support Airplay at all. Very disappointed although Hulu+ somewhat fills that void. Just my 2 cents