I've had it happen twice while using the standard battery, but haven't seen it again since the first weekend of its release. (Of course now that I've said that, I'm sure I'll see it within a few hours.)
I've had this happen twice too. Once while it was in my pocket and brought it out to check it and it happened. The other time it was sitting overnight and when I woke up it happened with the LED still blinking for a notification.