My two sons (ages 17 and 20) spent 5 days at La Luna over Christmas week 2012. We absolutely loved it and will definitely be back!
PROs: the food (see separate review of Las Estrellas, the excellent restaurant we ate most meals at); the staff (super friendly and helpful); the ambience (laid back, uncrowded, just what we were looking for).
CONs: None for us, but for some travellers I could imagine that the lack of a pool might matter (it would have to us when our kids were younger, but not now); lack of AC in the cabanas meant that the upper level got pretty hot at night.
We arrived on Christmas Eve and were warmly greeted by Luuk, who was a constant presence during the week. He and the rest of the staff are just so warm and pleasant. Christmas Eve was a special three course dinner with a pinata afterwards - the entire staff and their families were there, giving the whole thing a really fun holiday feeling.
The room we were in (Captain Dale's Quarters) was just fantastic - about 150' from the ocean, with the calming sound of the surf a constant relaxing background. A breeze blew pretty much constantly, meaning the shaded deck and lower level were always comfortable - despite temperatures being pretty much constantly in the 80s during the days, 70s at night. The upper level, where my boys slept, got a bit warm at night because the breeze doesn't come through as well. They also had a bit more mosquito action - I had only a couple of bites on the lower level and didn't even use my netting at all.
We went to the ruins one day and Luuk told us at dinner the night before to be sure to get there by 8:30 AM before the buses from Cancun arrive around 10 - good advice. Another day we went to Atumal to go snorkeling (about a 30 minute drive towards Cancun) and one other day we did a kayak trip in the Sian Ka'an biosphere nearby - the staff made reservations for us on the sunset trip that leaves at 3 PM - we were back by 7 PM.
Almost all our meals were at the fantastic Las Estrellas restaurant that is part of the hotel. A simple continental breakfast of very good coffee, a plate of fresh fruit and toasted bread with jam and butter is included in the room rate. Other things including my son's favorite, french toast, is available to order a la carte. There is a full bar.
On Wednesday night, there was a BBQ with live music (which was just OK - the tough grilled skirt steak was the only miss on food all week at Las Estrellas).
We went down the beach for dinnner one night to La Posada de Margherita, recommended by my guide book, and the food was good (fresh pasta and fish) but the ambience was far more rushed and hectic than Las Estrellas. We ate a lunch at Akumal the day we snorkeled at the very good La Buena Vida, recommended by the La Luna staff.
For one son finishing college applications during his HS senior year and another who is pre-med in college finishing a very touch organic chemistry class, plus a dad coming off a busy work schedule, this was just what we needed. We joked that the theme of our week was "To The Hammocks!" - because after having breakfast 100 yards from our cabana, we'd usually return and the boys would each take a hammock, break out the Kindle and books, and just read, while I'd walk the beach, join them at the comfortable bench on our deck or sit down on the beach and read.
The night before we checked into La Luna we flew into Cancun and stayed at the Ritz-Carlton in Cancun. The night we left La Luna, we drove to Paradissus (an all-inclusive resort) in Playa del Carmen. Since it was our first real visit to Mexico, I wanted the boys to get a taste of both flavors - the luxury resorts and what I suspected we all would prefer, the more laid-back beat of Cabanas La Luna. By the end, the verdict was unanimous - Cabanas La Luna beat out the Ritz and the Paradissus easily. "This place is kind of soulless," I remarked to my son as we walked around the spacious grounds of Paradissus in Playa del Carmen after leaving La Luna. "Yeah, I miss La Luna," he said. The best endorsement for a vacation I can think of!