The location is perfect. The Graca area is far enough from tourist and business bustle, but it's a real neighborhood. No Metro stops are very near, but the famous #28 tram runs past the door, there are buses close, and Uber is everywhere in Lisbon.
The flat is on the third floor. This may sound like a disadvantage (Lisbon has enough hills as it is!), but it turns out to be an advantage, minimizing street noise. The front of the flat is on a big street, a normal city avenue. The back of the flat, with a nice view looking out at the river, is quite quiet.
The Brothers are first-rate hosts! They gave me all the guidance I wanted, so I wasted NO time in my one-week stay.