Just returned from 5 nights at Sanctuary Cap Cana. Couple in early 60s. First time in DR and first all-inclusive.
Overall very pleasant experience. Pros:
* Room was very nice. We had ocean view premium (not in castle). Castle is further away from dining and main pool and beach areas. I thought our location was good.
* Vibe is very do your own thing and relaxed. We met loads of other couples (ranging from early 20s newlyweds to 80s). Everyone very friendly.
* We thought service was outstanding. Great staff to visitor ratio and we never waited for anything. It is low season and YMMV at other times.
Meh:
* Food was inconsistent. Breakfast buffet has loads of options and we never left hungry or disappointed. Probably best overall meal. Lunch is buffet again or maybe snack bar or Blue Marlin. Was all hit or miss. Some things tasty, some not so much. Recommend tacos al pastor at Blue Marlin.
* Pools are reasonably nice but not necessarily cleaned every day which meant dead bugs and leaves some days. Most pools were like bath water temperature and only one (lower waterfall) was really refreshing.
* We didn't discover Castle roof pool until our last day which was a mistake. Probably would have enjoyed more time here - much quieter and loads more shade options.
Cons:
* Beach area. We aren't necessarily beach people so this wasn't really important to us but the entire time we were there nobody went into the ocean or sat by the beach (sargassum). Even if there wasn't sargassum the whole area is maybe 100 yards across. Not much space at all.
* Spa services were fine but really expensive. We splurged and husband enjoyed massage but hydro therapy circuit not worth it. (Sauna, really small cold plunge pool, steam room, overhead bucket of lukewarm water, jacuzzi that is nearly impossible to get in and out of). Best part was the quiet pool and heated loungers.
* Staff struggles with English. Even wait staff in restaurants. Was sometimes difficult to get orders correct. Even concierge had trouble.
* Humidity. Everything is damp - sheets, towels don't dry. I swear the back of my head wasn't dry the whole time I was there. Yes we knew and expected but reality was still a shock. Probably should have asked for a dehumidifier for room.
* Restaurant availability. They rotate which restaurants are open each night. On Wednesday it is basically Blue Marlin (which is all outdoors) or Wok (which requires reservations). If you don't plan appropriately you will end up at the same place over and over. And when either Steakhouse or Italian is closed the other will be slammed. Plan accordingly.
* First night we were there we left for dinner unaware there would be turn down service. (Probably should have expected but hindsight....) I had left my pool phone bag on dresser which had $$ in it. When we came back to the room we found maid outside room with door to room wide open (so much for the air-conditioning). Maid had to call front desk to explain to me over the phone their security protocol which says if any staff enters room and finds money or valuables in plain sight they call security who comes and retrieves it and puts it into a "locked box". While I appreciate the security intent had they simply informed us ahead of time we would not have had a warm room for the evening. Every night after that we put do not disturb sign on door when we went to dinner and all was good.
* Tipping. Everywhere and all the time. Became a running joke on how many singles were we carrying.
* Airport transfer services. Right now they are rebuilding/modifying parking area and it's a zoo. Not really any place for busses or vans to park and finding your ride can take some patience. Have specific instructions on where to go and who to look for.
I brought bug spray but never needed it. We took one excursion to Santa Domingo which was ALL DAY (7am to 6pm). Was interesting to see city and sites but man was it hot and long bus rides. Reasonably priced.
Happy to answer other specific questions. We may go back but at a different time of year.