I have been flying internationally with my PRS-600 and then PRS-650 for at least 3 years. And I fly a LOT.
I have it in my carry on bag, I have never taken it out of the bag, and only one had to take it out. And that was CDG (Paris) and they wanted EVERYTHING electronic out of the bag, including cables. After I was about half way through, they said to stop, it was OK, but I continued, until EVERYTHING was out. Then I stood in the way and put everything back, in its proper place.