I just did my GE enrolment on arrival. Was supposed to be LAX but got rerouted through SFO as my flight from OOL was delayed.
They have implemented it really well. You are allowed to use the global entry line for enrolement - many others have said other airports make you use the normal line first.
So straight up, did the standard arrival questions, then asked to put my name on a list and sit down. I was #2 of names not crossed out. Within 5 minutes I was called up (to a standard immigration booth, not a back office), simple questions plus checking drivers licence and scanning fingerprints.
All up it was 20 minutes from aircraft door to being outside the terminal. The rest of the non-Americans on the flight would have waited an hour at least, the hall was chockers.
Just waiting on the final email with my KTN.
Edit - got my KTN just under 3 hours later.
