Some of the down sides are you cannot come out of the airport and "Grab a Cab" taxis are not allowed to operate inside the airport unless they are dropping off or have federal permit to work for the ground handlers.
Bus service is available but only to the bus terminal on Tulum Ave in Downtown Cancun and Playa Del Carmen Bus Terminal. The service is inexpensive but very inconvenient if you are staying in the hotel zone.
Cumulative Transportation is sold as you exit with your bags but for $12 US per person you have to wait til they fill the vehicle and then depending on where your hotels are located get a tour of Cancun so a 20 minute ride to your hotel can become 90 minutes waiting and riding.
