I think if you average out the reviews of this hotel, and read the comments, a 4.2 out of 5 is exactly what you get, and actually for most of the reasons remarked on by others.
This is a fantastic holiday location - and I will get to the reasons on the PLUS side after I reference some things that are a little less than perfect.
First amongst these is the beach - sure there is a beach and the sand is white talcum and the water is azure blue and turquoise. However, there is an unsightly breakwater that I found disappointing and areas of it had some rocks you had to manoeuvre around (luckily with crystal water you can see where you put your feet). There was a daily dose of seaweed - but this is obviously neither the fault of the hotel nor exclusive to this resort. Bizarrely I didn't mind the weed too much as it was not slimy or smelly - and the beach workers who cleared it up worked manfully to make the beach the best that it can be. However, if the beach is your prime motivator, probably not going to be for you.
Second - this resort is MASSIVE which is good in the way that you can try a lot of different locations, bars and restaurants, but it is a task to find your way around. There are frequent and comfortable road trains, but for me the signage could be clearer, and the trams better identified so that it was obvious which "loop" the tram was headed on. you get a map on arrival, but the map is small print to read, and useless in the evenings as it is too dark to use the map. Anybody that you ask for directions is super helpful, and you often get asked if you want a "lift" by kindly drivers - BUT I had frequent episodes where I was confused and lost.
I heard some folks complain about the booking of the a la carte restaurants - but I followed a previous traveller tip and booked in advance of my vacation, and everything was super slickly handled.
Okay nit picking over - now onto the good stuff!
The hotel grounds are beautiful - a tropical oasis with iguanas and exotic birds and beautiful plants - gardeners do a great job.
The room I had (Block 6) was comfortable with a huge bed, seated area and balcony overlooking the jungle. Maid service was impeccable - (2 beer cans in the fridge are the only booze - but there are so many eating and drinking options that I was perfectly ok with that). All rooms looked similar high standard.
Pools were large, clean and surrounded by bars wash rooms and lots of beds and shade. Swim up bar was great, and the bar staff were ALWAYS friendly, polite, quick and fun to chat with. there are a few smaller pools dotted around - I particularly liked the small pool with 3 whirlpools and its own bar surrounded by cabanas for shade (near blocks 4-6). Towel service is easy and readily available.
Restaurants were great - we ate at the main buffet restaurant mostly, which had an amazing choice of food and the nicest possible waiters for whom nothing was too much trouble. I like my food hot (both spicy and temperature) and I noticed that there is a microwave located near the mexican food section that allowed me to heat my own plate (I really appreciated that). For breakfast there are egg stations that make the best freshest omelettes and eggs with the ingredients that you choose - again wonderful.
We went to 3 a la carte restaurants - and in ascending order were ranked as 3. Tequila Mexican located in Tulum (okay) 2. Mikado Japanese and hibachi "show cooking" (very good) and 1. the Gran Tortuga Brazilian Rodizio (awesome). I met some friends there who also went to the Gourmet restaurant - said it was good, and the Mashua Peruvian fusion restaurant - which they said was awesome.
In ALL the restaurants the service was wonderful - and Cannot say enough good things about the hotel and management.
Which brings me to the last thing - which is the hotel staff from gardeners to porters to bar and restaurant to maids and management - THANK YOU!! You do an amazing job! We had only a couple of questions and one minor room issue to discuss, and the way that we were dealt with was truly 5 star - quick, professional, and made us feel really valued and special. We had a great stay and would recommend this complex very highly (as long as the beach is not your highest priority)

This is a very large resort but easy to get to know and get around. We had full access to all restaurants plus The resorts Tullam and Akumal. Even the buffets were quite tasty......good variety of foods. They have 2 pools, 1quiet and the other activity driven so very loud. The staff were very friendly and accommodating. Worse was we had to get up early for chairs at the pool..... would definitely go back!!!

From March 24-31 2018 I traveled to Principe Coba with a group of 7 family members. I can honestly say this is the best vacation I have ever been on.
I mostly stayed at the entertainment pool at Coba. The entertainment staff is amazing. They had high energy and they really got everyone involved in the activities that were being held. All of the entertainment staff were great, especially Gigi, Andrez, Mauricio, and Carlos were truly great at their job and seemed so excited and enjoying their job. The activities at the pool were fun for all ages. People of all ages were involved. My vacation wouldn't have been the same without these workers and activities.
The beach was okay. Staying at Coba we had to take a 4-minute trolley ride to the beach. We never had to wait more than 10 minutes for a trolley both ways. The beach was small but I didn't really mind. There were workers in the morning whose job was to get the seaweed out of the sea. These workers worked really hard. The snorkeling was really good at the Akumal beach. If you are a snorkeler I would recommend going to the Akumal beach as there is more fish. If you are staying at Coba/Tulum you can't use the Akumal beach chairs but you can swim/snorkel in that area.
The food was really good. I am a picky eater and I found something every meal at the buffets. If you are looking to eat at ala cartes make sure to book them early to get the best choices. All of the restaurant staff were hard working. Especially the ones at the bigger buffets. However, they were all friendly and made sure everything was 100% at our meals. I have to give a shout out to the workers at the Tulum and Coba buffet. Really busy but still amazing service.
If you are someone who likes to be at the center of festivities, I would recommend buildings 30 or 31. These buildings were near the activities pool.
The workers at the front desk at the Coba lobby were really helpful. Yazmin Sanchez was really helpful and good at her job.
The resort was very clean and there were workers always cleaning.
I only have one complaint which is:
-There is a dolphin aquarium with several dolphins that were captured from the sea that you can swim with. These dolphins were not rescues. I can't believe some people participate in this. Dolphins belong in the sea, not small pools. They dolphin pool was close to the ocean. It must be hard for the Dolphins to hear the ocean at night. Please avoid this attraction as it is not humane.

In conclusion, I would highly recommend this resort to people of all ages. The workers were all really excellent at their job and truly made you feel special. I would go back in a heartbeat.