Martin's place is perfectly located, very close to the best spots and walkable areas in downtown Lisbon, but on a quieter side street to avoid the worst of the commercial district noise. All of the buildings in the area are very old, but Martin keeps the apartment well appointed and immaculately clean.
The only downside from our view was the elevator. You must climb 18 wrap around stairs to get to the first opportunity to get inside, and it was too narrow for our stroller without folding it up. Other than this it is a great spot for families with young children.
I would definitely recommend staying at Martin's place.