Pedro's place is very well located and within very close walking distance to all the key points of Sintra. It also has shops and amenities within less than 5 minutes walking. Sintra is a very nice part of Portugal so the surroundings are outstanding!
That being said and as Pedro himself has written, it is a "Grandma's House". Complete with the old furniture the grandma must have received as a wedding gift :) As others have described, the apartment is located in an old housing block the building is not beautiful but perfectly fine and safe and inhabited mostly by other grandparents. It has 2 small balconies and there are views of the hills in the distance which is nice. The kitchen has a stove, large fridge and microwave but the utensils were very old scratched with rusty pans not suitable for use so it's better to eat out if staying here. There was no soap, salt, pepper, hand soap, dish detergent, cleaning products, or basic essentials in the apartment so your first trip will be to the nearby grocery store to buy all the basics. The place was fairly clean except that it has so much large furniture and cabinets that upon closer inspection we noticed they were covered in 5-10 cm of dust. I only noticed because I started to have dust allergies and wondered what was causing it. The living room is decent and it comes with a new TV which you can connect to Netflix which is one nice comfort to have. The beds are old but comfortable and large (one is a hard orthopedic mattress & one normal). There was a good supply of towels and linens stored in grandma's cabinets.
Overall, I would recommend the place if the price is right & you are looking to crash a few nights and spend time outdoors exploring Sintra & it's surroundings.