Even though I have used my Global Entry (GE) for several years, I still keep at least one of the blue USA immigration forms in my backpack as back-up.
When returning to the USA, if at all possible, I try to schedule at least 2 hours between this first set of connecting flights returning to the USA just to allow time for all of the challenges that might occur with immigration, customs, waiting for luggage to take for recheck, getting to the bag recheck area, going back through TSA to get to my next flight, being behind the idiot in the TSA pre-check line that can't seem to get the coins out of his pockets, etc...........
If the San Juan (Puerto Rico) airport is your port of entry into the USA, currently it is much FASTER to just fill out the blue form and get in the regular immigration line. As of 4/30/16, the SJU airport only had two of the Global Entry kiosks, and one has been broken/closed since at least my trip thru there in September 2015. Unless you are one of the first three people in line for the one Global Entry kiosk, it really is faster just to go through the regular line. (Yes, it's possible that the broken one could have been repaired by now).
Earlier this year (Jan 2016) my port of entry into the USA was Dallas, which usually is a fast and easy Global Entry. I saw several people in front of the machines with worried looks and trying to find a human, but I passed them by to use another machine. {Note to self - pay attention in the future}. Once I finished the automated Global Entry process, then I understood the confusion. THERE WAS NO PAPER in 9 of the 12 machines & no staff anywhere. Once you use Global Entry, you can't use the automated system again for 24hr, so it's back to using the blue immigration form. However, the horribly long regular immigration line was my main concern, so I grabbed the blue immigration form and along with my Global Entry photo identification I went straight for the Global Entry short line and exit. The officer almost didn't accept the blue card in this line, but there were more than 14 of us (including crew) with the same situation so he let us pass. {This “no paper” in the kiosks has also happened in MIA}.
BIG HINTS: If you have Global Entry, take a photo of this card AND your passport to keep on your phone. They will NOT allow entry into the USA with these electronic copies, but having the copies will help you fill out the paperwork if the originals are ever lost. Take photos of your entire travel schedule and your dive cards. This way you will have immediate access to all of your important documents even when you don't have access to internet or cell service. Yes, use your phone to take photos of your luggage before check-in at the airport since this can be quite helpful when trying to fill out lost luggage reports.
So why endure all of these travel headaches? THE DIVING IS WORTH IT, especially if diving with the great trips hosted by SD.com.