When flying internationally, I generally fly in and out of SFO. Generally, SFO is well staffed and immigration lines are short, but I love the idea of circumventing the queue when the lines are long. Here are my most recent Global Entry experiences:

#1: Flawless
#2: Had to wait in line to get to Global Entry. Would have been faster to use a live agent.
#3: GE OK, then random customs inspection. Full bag unpack/pack.
#4: GE OK, then random customs inspection. Full bag unpack/pack. Agent found an apple in my laptop bag that I got on board the Virgin Atlantic flight and forgot to dump. Gave me an extended shaming about how I could lose my GE. Fair enough, I was trafficking in non-GMO UK apples, who knows what this could do to Cargill's valuation.
#5: Line at Global Entry. Then I got the random secondary screening, had to wait in line to get reprocessed. Would have been faster to use a live agent. Also I had to go customs inspection. But this time they only scanned my bag, then didn't fully dump it out.

So I'm beginning to lose interest in GE. While I know that officially there's no connection between GE and customs, my hit rate for customs in previous years was closer to 1 in 10. It feels like "Hey Mr. earlybird off the plane, not so fast, we've got a lot of customs employees with nothing to do!"

In future, I'm going to make out the immigration form on the plane and skip GE if the immigration lines are short.