I don't like streaming to my ATV because, half way through a film, my Macbook Pro goes to sleep and the ATV suddenly stops. So I have to go into System Prefs and switch off the sleep timer. Then a couple of days later I get back from work to find my MBP has been on all day. So I have to reset the sleep timer again. Then a few days later I watch a film on my ATV... well, you get the idea! So have Apple sorted it so the Mac knows it's streaming to the ATV and temporarily disables the sleep function?