LOVE Global Entry. We used it the first time coming back from Turkey last week. No line at all at JFK at the kiosk. Yes, we did have to wait for luggage, but that was ok. And (I didn't realize this then), you don't have to fill out that customs form they give you on the airplane. You just type your answers in at the kiosk. Super easy.
We flew down to Houston to get ours on a Sunday as I didn't want to have to take a day off work, and I wanted to get it before our next trip. Flew down, had lunch at Pappadeaux's, did the VERY quick interview with fingerprinting and eye scan, flew home. Hardest part was filling out the online form that asks for every country you have visited in the last 5 or 10 years!