This Lisbon flat had some nice qualities. We were three and it had two bedrooms and plenty of room. In addition there was a sitting room with a TV, kitchen, and a good bathroom. It was one floor up in a four story house so it only involved a few steps up.
There was no table in the kitchen which meant that we fixed up breakfast and some evening snacks during our five nights and ate in the sitting room over a coffee table so this was a minor point once we realized there was no place to eat in the kitchen.
If you have mobility issues or really heavy baggage then please realize that no matter how you approach this nice flat that you will be walking up some steep streets since the flat is on a hill. A taxi would be your best bet. We walked up but that is normal and easy for us.
In addition the bedroom closest to the sitting room does not get very dark. The curtains are white and thin so street lights might keep you awake if that is a problem. It did not bother me but my wife was affected. The second bedroom is much darker.
All in all, if you are not bothered but the climb uphill this is good place to stay. Walking downhill from the apartment is a crooked walk to Rossio Sq and then you are in the center of Lisbon and metro and bus stops.