My wife and I just did our sun run for the winter at the JW Marriott Cancun. We used points for the room and paid the upgrade to Club 91. We were there Jan 8 -12.
For those who want the short version-
Overall: 4 1/2 out of 5. Positives were the service, sun, grounds. Negative were the airport pick-up (see below), 12th vs. 14th floor room, beach, drippy faucet in bathroom. Club 91 may seem pricey but for 2 people it is worth the
added luxury and the discounts offered for use of the rest of the property.

For rest of you-
Arrival: I received an email about a week in advance of our arrival to the JW explaining the details of Club 91 and the cost involved. The cost had dropped from $120 at the time of booking to $100 now. I think it might have to do with the low occupancy rates. Also the email asked when we would be arriving to the airport to schedule our pick up service and if we wanted to schedule any activities while we were at the property. We didn't plan ahead but if you wanted a golf time or other excursion, the concierge at Club 91 could plan all this for you before you arrive.
At the Cancun airport things have changed over the past 5 years. Mostly in the growth area. Immigration can now be reached after disembarking on a jetway to inside. The lines for immigration are long and slow. We picked the
wrong line and got stuck behind a non-latin alphabet using non-spanish/english speaking couple who did not understand the forms or instructions. After finally clearing immigration there was more waiting (30 min) for our bags to begin to come to the claim area. And clearing the customs is still the same quaint process. Push a button and if it is red you get to open your bags including carry-ons for inspection or green and pass go. I lost and
got a red light
After clearing customs, the airport authority has cleaned up the greeting area. Now it is licensed vendors in booths and airport employees only. Outside the doors are the authorities have set up little fence to keep the
ride hawkers back from the passengers. Now as an arriving passenger you have hope of finding your ride before being swamped by huckster. Our situation was not so great. We took a sweep of the area and could not find the Marriott guy. After waiting about 10 minutes we finally found the sign but the guy kept ignoring us. He was focused on another couple so we kept following him. He finally stopped and we were able to get a ride. But not before he found a third couple to ride in the van to the JW. So do not expect a private car to the hotel. It is the same van experience that I have had with other tour operators.

Check-in: Arriving at the hotel was a much better experience. We were greeted immediately upon exiting the van. Our bags were quickly taken and we were escorted to the Club 91 lounge for check-in. Along the way we were given a mini-tour of the hotel lobby area. The lounge is on the 14th floor. When we entered the lounge we were greeted by name. Our check-in was a smooth process. The specifics of the Club 91 offerings were explained to us at this time. Five food presentations Breakfast, Lunch, Tea, Dinner/hors d'oevures, Dessert. A happy hour from 5 to 7 with free alcohol. We were then escorted to our room on the 12th floor with a south view. The Bell-man gave us the old school tour of the room and even included a safety briefing for emergencies.

Room: The room is what I thought to be standard sized. About a usual King, non-smoking Marriott room. The bathroom however made up for the average room. The BA was a dual sink vanity with separate stool, shower and tub. It is the nicest Marriott or any hotel BA we have seen since our stay at the Renaissance Brussels. The king bed had new bedding and a pad (not memory foam but a cushion) on top of the mattress. A nice soft bed. The flat panel TV was shiny but without HD service it is nothing special. The channels were a mix of spanish language and subtitles with english language weather channel, CNNHN, and ABC. The balconey was definitely an upgrade over the
other balconies. It was quite large and the southern exposure made it an asset. The low sun and high tower put the beach and pool in the shade by 2:30 in the afternoon so the deck added to our sun time.

Pool: Pool was big. It was a free form pool that offered lots of space to spread out. The hotel provided towels and lots of lounge chairs. There are umbrellas in the pool area but due to the wind (30+ mph almost the whole time) the umbrellas were closed. Bar service was available chair side. The waiters let you know who was supposed to serve you but if you did not need anything they were not always bothering you trying to sell you somthing. The
prices were not Mexican cheap but were Resort modest, $6 USD for a beer and $8 for a blender drink.

Beach: Big downer. The rumors of the government dredging in tons of sand to make a new beach may have been overblown or nature is a stronger force to be reckoned with. The beach in front of the JW was about the smallest that I could see. It was about 25 feet sea wall to average water line. During our visit, there were workers building what appeared to be a rock erosion wall to try and save what was left of the sand. The sand did have number of palapas with lounge chairs for use. And there were beach shacks for lack of better term. These were platformed areas with a thatched roof. The shacks did have some uncovered area for sunning and could easily fit 6. I don't know if they were 1st come or available via reservation. It was not an issue during our stay.

Club 91: Pleasant and definitely worth the upgrade. When we entered the lounge we were greeted by name. Breakfast fare was the usual C-lounge type items. If you see the coconut french toast, load up. It was by far
both Mrs. Cayenne92 and my favorite item. Lunch was usually 2 cold salads, sandwiches, cheeses and desserts. Tea was cookies and sweets only. Dinner was a taste from one of the hotel restaurants. Nothing special in our opinon but kept the hunger away. Dessert was more sweets. The lounge offers bottled water, Pepsi, Pepsi Light (diet Pepsi in the US), 7-up, squirt club soda, coffee and tea. The happy hour was alcohol served by staff. I never heard a blender while in there so, I don't think those were possible. Also pants were strongly encouraged after 5pm for men and similar attire for women. I don't know about the internet connection as we were on vacation and did not bring a computer.

SPA: Great. Everyone there was professional and courteous. Mrs. Cayenne92 had 2 massages and a cut and style and I had a massage also. We both enjoyed our treatments. Because our reservations were made through Club 91 we got a 15% discount. Also the fitness area is located in the spa area. It was good sized and had enough aerobic equipment. There were also free weights to 50 lbs and a safety rack for bench press and squats. I never saw any classes but saw the room for them. The second level of the spa had the locker rooms. This is area Club 91 gets you into for no charge. The locker rooms had single sex Jacuzzis, a steam room, a sauna, showers, and a waiting area for pre- and post treatments.

Restaurants: We only ate at the poolside cafe the Beachwalk. The menu was simple cafe and served a large amount of food. It was well cooked and the service was prompt and friendly. Also we went next door to the Casa Magna and dined at La Capilla, an Argentinian style steak house. The salad bar there is worth the visit. I was tempted to just order that, as Mrs. Cayenne92 did but I was glad I enjoyed a cut of meat also. The meat was very tender and prepare the way I like it. The service though was flaky. At times in the same meal the waiter was prompt and ready to serve but would then disappear from the restaurant for a long time at a shot. By booking a reservation through Club 91 we got a 15% discount on the meal.
La Dolce Vita is across the street from the property. It is a nice typical Italian restaurant. The food there was above average and the service was outstanding. The live jazz was a strolling saxophonist playing to recorded tracks, pleasant and not overbearing.
Room Service: Great. The food arrived fast and hot. The servings were good sized. We highly recommend the La Mexicana dessert. It is ice cream in a caramelized tostada-like shell.

Construction: The stories are out of date. The JW has finished all major construction as we could not see or hear any. There are some rooms being worked on but we only noticed because of the workers and tools near the rooms. The drilling sounds people have reported are most likely their neighbors opening the balcony doors and leaving them open. The Casa Magna is having some work done on its skylights but that is all we could see. To the north, they are building a new hotel, Cancun Palace. The work on that is about 80% complete and the sounds could only really be heard when near the property and outside.