I just re-entered the US via JFK last night. There was an employee going up and down the line promoting "Global Entry" (skip the line). All I could think was how utterly farcical the whole thing came across.
The trade-off is: they do a background check and take some biometrics, and in exchange you can skip the conversation with an immigration agent where they ask you where you're been, etc. - you just answer the usual customs-form questions at a kiosk.
It's actually a pretty reasonable trade-off, and speeds the process of going through Customs - which, unlike some of the TSA stuff, is in no way unique to the US (having gone through immigration/customs in 20+ countries, I can say with some experience that the US is far from the worst...)