I use Safari to watch Netflix movies and the video almost always freezes after about 30 minutes and I can only press the power button for 5 seconds to restart, nothing else works. I tried it on battery and AC, no difference. It happened with 10.7.4 and now also with 10.8. I never had this problem with my 2008 uMBP. I'm past the 2 week return period, from past experience, might Apple replace it anyway?