anecdote: arriving at IAH today from LHR nearly the entire flight crew of my plane hit the GE kiosks plus many pax hit it as well. For the first time I saw nearly all of IAH's15 kiosks full. I didn't have to wait but the entire row was nearly filled up with more arriving pax hitting them behind me. that was a first for me to see and I use IAH usually at least a couple times a month.
They claim IAH has the most kiosks and is the "leader" in Global Entry but for the first time today it really looked packed.

At iah They are also really pushing and advertising the one-stop connecting flight immigration service letting in-transit int'l pax and those with no checked bags skip the long lines. Are any other US airports getting on the one-stop bandwagon?

as an aside we did have to wait while armed DHS CBP "cops" and a plain clothes (not suit just biz cas) came on and "escorted" 3 people off the plane. That had people looking around and chatting.

Also at LHR they had the UK border agency doing outbound checks at the desk before security at Terminal 4. Quite annoying guy checked my passport. It seems one is supposed to be "chipper" with then as he berated me for not being cheery and polite. I wasn't rude mind you, just blunt and non-plussed.
Am done ranting, time for sleep.