I've had it twice connecting DOH-USA on QR in J. The secondary screening at the gate has a line for business class passengers and OneWorld elites. They'll always ask to see your boarding pass, and they'll note the SSSS, and just ask you to step aside once through the metal detector. Some basic questions, a quick manual search of your bag (sometimes they'll take things out, but they will help you re-pack), and not much else. Nothing to be nervous about. They don't take you to another area and, in my experience, are always very kind and helpful throughout. Takes about 5 min.