The only thing I really dislike about the ATV is how long it takes to stream videos shot on the iPhone/iPad to it. I wanted to watch an 11 second video of my kid shot on my 4s over airplay on ATV, it took almost 2 minutes to load an 11 second clip. I really can't understand it. I assume it's some sort of video conversion, but I don't know why movies would just be saved in .m4V format on the phone. Also, ironically, you can go under video and stream an HD movie from there and it will start playing almost immediately with 2-3 seconds of buffering time.
And to circumvent issues people will raise
I have 4 ATV's including the new gen and they are all that way. I have the newest Airport Extreme. It happens with other routers and from all iPhones I have including 4 and 4s. This is an ATV that is 3 feet from the Airport.
Oh, when streaming music from my Mac Mini to the ATV's it occasionally breaks the audio stream as well.