Great location. (1)However, use landmarks to remember where the apartment is and to orient- maps apps are less dependable than usual & the streets are steep
(2) Quite a climb up the stairs if you have heavy luggage, and the entryway to the building could be dark (3) open the skylights for air(4) visits to the non-tourist parts of the city are a good change if you have time , including for supermarket runs - a Lisbon Card transit pass is good value & takes you to Cascais and Sintra as well