I had some good and bad experiences with Go. They seem to be better when picking you up at the hotel and taking you to the airport than in the other direction. The New York Go was great arrived at the time given and got you to the airport in good time.
Late picking us up but got us to airport with plenty of tine spare
The journey from our hotel to JFK airport was not a good experience. The shuttle that was booked (for 2pm) the day before departure did not arrive. The explanation was that the driver had gone to the wrong hotel , the operator said that they would guarantee that we would be at the airport by 4pm, a replacement shuttle was sent one hour later. Due, mainly to traffic, but additionally due to the driver struggling to get the last two passengers luggage in, it took 2 hours to reach the airport ( this time being three hours from our original pick up time.