First of all, we had a great time in Lisbon in Joao's guest house. Joao is very helpful and waited for me late (1 am) on a sunday night to welcome me, and I'm really thankfull. The apartment is exactly as it appears on the pictures, but the thing you can't guess is that the living room is very bright and sunny the whole day ! The neighborhood is fantastic, quiet, a lot of charm with the steep paved streets, and very close there is a small shady square, with a supermarket and restaurants (btw Pao de Canello is a great place to have a brunch on a terrace !). And finally concerning the location, you're about a 7 min walk from the Rato metro station, and a 15 min walk from the Baixa-Chiado (in other words : everything is in a walking distance !)
Then concerning the apartment itself, it is very convenient with the two big bedrooms, and the great living room. The kitchen is very nice and functional, as is the bathroom.
I stayed there for 1 week with my wife and 18 months baby girl. Joao provided us with a baby bed, and it was perfect. We had most of our meal at the apartment, and we really felt like we were home.
So I can only strongly recommand this place, and there is a great chance that if one day we go back to Lisbon, we will stay at Joao Guest House again !