We stayed at the Aquae Sinis for a week and were very satisfied overall. The concept of the albergo diffuso was not a problem at all as the three buildings are located within easy walking distance of each other. We especially liked the really charming atmosphere of the hotel with lots of lovely details and typical Sardinian decor. A big plus are also the pool and garden areas and, as so many reviewers have said before, we absolutely loved the rooftop terrace where breakfast was served (definitely above Italian standards).
That said, it nevertheless didn't feel like a 4-star hotel but rather like a b&b with some perks and rustic atmosphere. For example,in 4-star hotels you expect to have warm water for showering throughout the whole day, not just in the mornings when the hot water boilers are full, or the walls to be thick enough to not hear every word from the neighboring rooms. Don't get us wrong - we are not a particularly picky guests and are fine with basic facilities, but other guests will probably be dissatisfied with these things when the expect 4-star standards.
One thing that needs to be mentioned (even though it is not directly associated with the hotel) is that it turned out really difficult to find eating options in Cabras. The hotel itself doesn't seem to have a restaurant anymore; at least it wasn't mentioned to us in any way. (Only on one evening there was a special Sardinian dinner with music on the terrace for a group of American guests, but that wasn't open to others. We actually found it rather annoying because our room was directly below the terrace and we felt that this should have been considered or at least mentioned to us.)
We ended up eating at the same pizzeria three times during our 1 week stay and even went to a supermarket in the outskirts of Cabras one day to buy ourselves some pre-packed sandwiches because we couldn't find a place that was open. We did see several restaurant signs in the center of Cabras, but most of them seemed to either point to long-closed restaurants or to places too far from the center to get there by foot.
Altogether, we were satisfied with our accommodation choice as it was a good base to explore the west coast of Sardinia, but not more. A car is absolutely mandatory because after a day in Cabras you have definitely seen everything there is to see.
This review is the subjective opinion of a TripAdvisor member and not of TripAdvisor LLC