I've noticed an issue with my N4 freezing up and the buttons becoming unresponsive in the past few days since the 4.3 update. It's happened three times now, once during a Netflix playback and once during a YouTube playback (in that case the sound was still going but the video stopped and the buttons were unresponsive). I think the other time the screen was off and it wouldn't come back on. Each time I've had to do a reboot by holding the volume up and power button. I'm probably going to start going through my apps and checking if there is something incompatible, but has anyone else seen something like this yet?