I just went through the preclearance. We flew first from AUH to LAX and I paid for the Gold Departure service (through the EY website) and it was well worth it. We checked in at the first class counter and we were escorted to the first class lounge. The escort came back for us and took us down to security, moved us to the front of the premium line, waited for us while we used the Global Entry Kiosks then took us to the front of the line (in front of all other passengers) at to the xray machines and then to the last check point where they stamp your passport. I highly recommend using this service, worth the money!