Amazing location if you're looking to relax. You're surrounded by peace, quiet and amazing views of the Douro Valleys. The pool area is great in a warm and sunny day and we enjoyed walking around the property in between the vines and the apple trees (the girls found it incredible to taste fruit after picking it up themselves). Breakfast is decent (the coffee was particularly good) although I would encourage a broader offering (there were no lactose free choices, for instance). Overall, it was a very good experience and I would happily go back.
Planning a relaxing trip? Staying at a spa hotel can make your experience even more enjoyable. Quinta da Portela Douro (from PLN 377) is one of the best hotels with a spa in the area.