SFO Global Entry Interview ~20mins
I did mine at SFO and it took about 20 minutes. About 15 minutes of it was reviewing some information about my travel habits and about 5 minutes of going through a mock exercise on learning to use the GE machine.
This has been one of the best rate-of-return things I've signed up for as I have saved many hours breezing through customs. (I also believe if you have GE, Canada will reciprocate with free Nexus. I'll look into this further for my next stop through YYZ).