We really enjoyed Katia's apartment, we were 5 guests (one couple + 3 singles) and there was plenty of room for all of us, with enough privacy for all.
The apartment is lovely, pretty big, with nice wooden floors and nice modern kitchen with pretty much everything you need.
We really liked the area too, close enough to Bairro Alto and to main transportation, and its an authentic neighbourhood with little alleys, traditional little restaurants etc.
Katia the host was very helpful and even replaced a mattress with a brand new one after a complaint that the existing one wasnt comfortable enough...
All in all, a very recommended stay in Lisbon!