I got caught in the back-up - NEXUS helped, but not 100%. As the above poster noted, even with Nexus, I couldn't actually get to the customs hall to go through the (empty) Nexus machines because of the crowding upstairs. The minimal staff upstairs did not provide any indication as to what was wrong, so it was only when I got close to the escalators that I was able to bypass the line and head down. That said - NEXUS still cut substantial time (hours?) off my wait.