We arrived on UA from AMS about 1:40 yesterday. We stepped off the plane at 1:45 and boarded the shuttle to parking at 2:05. Twenty minutes total from exiting the full 777 to driving away.
There were about a dozen people in line ahead of us at the GE station. Plenty of kiosks open but a short bottle neck occurs with the two agents checking your passport and paperwork. There is a logistical flaw with the layout here.
You have to cross into a roped off area to reach the kiosks. This requires you to cut through the line of people who have already done the kiosk thing and are now waiting to clear the GE immigration agents. When the queue contains more than a dozen people or so, it gets jammed up inside the roped off area. The queue curls around in front of the kiosks making it difficult for new arrivals to get into the roped off area with their bags and get to the kiosk.
It's a very bad flaw creating a bad flow. For us, it still only took a couple of minutes to get through and head down to baggage claim and customs. It must be a real zoo when several international jumbos arrive about the same time.

We were carry-on only so headed straight to the GE customs exit. Maybe 30 seconds here and on out the door.

Granted this was early afternoon and we appeared to be the only 'heavy' arriving at that time. The regular pax kiosks had virtually no one in the lines and the baggage claim was a ghost town. Much different from July when I arrived to find a completely full arrival hall and a baggage claim where people were in queue up to an hour to clear customs AFTER they claimed their bags.

Overall, a great experience. Especially helpful after that eleven hour nonstop on a packed aircraft.