The appointments are only scheduled two years out and every single appointment in 4 different cities were completely booked.
For whatever reason, locations along the US/Mexico border have pretty much every appointment available. Fortunately I have my own plane and flew 325 miles away to Del Rio, Texas. I made a day out of it and made a couple of stops along the way to places I wanted to see anyway, so it wasn't a wasted trip.
The entire process there took all of 15 minutes. They take your fingerprints, photograph you, look at your passport, and ask a few questions about your residence, place of employment, etc. I didn't need any other documents besides my drivers license and passport. My Global Entry card arrived about 3 weeks later.
The Global Entry card really only works at land border crossings. For airline travel and TSA precheck you MUST enter the preferred traveler number on your airline reservation. If you are enrolled in the airline's loyalty program you can enter this once and it's done for all subsequent reservations. After that it prints on the boarding pass and you don't need to physically have the card, although it does work as a physical ID when passing through security and checking in with the airlines.
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