We stayed in the Cynthia room. I loved the decorations, and the bed was comfy. It was really cold out while we were there. The heaters in the room and the common room did great jobs.
The Five House was a scenic 10 minute walk from a variety of restaurants and small shops, and about a 25 minute walk to the Quinta de Regaleira. While you could potentially walk to the Peña Palace, it looked like a very long, steep climb and I wouldn't recommend it unless you are up for something strenuous. The Uber ride there from the Five house was reasonable though.
Filipe and Vera where very friendly and accommodating with lots of great information on local things to do and see. The breakfast they set up for guests every morning was the best Airbnb offering I've had yet, with homemade breads and jams, yogurts, fresh fruit, and more.
Overall, a great launching pad for our first, but hopefully not last, visit to Sintra.