We cannot speak highly enough of Antonio. The communications in advance and during our trip were comprehensive, totally polite and extremely helpful. He gave us a number of pointers for our stay there. The flat is in an ideal location to explore the city with amazing views of the river and the city. There are shops and resturants very nearby that are worth visiting, we ate very well during our time there.
The stairs to the flat are steep, so I wouldn't recommend it if you are seriously unfit or unsure of footing (also the case for Lisbon in general!), but otherwise you'll be fine. He also left wine for us too! He is a very nice man!