It is a great choice for a backpacker who seeks a good value place to stay. The rooms are rather small and basic, with only a tiny window close to the ceiling. Not terribly soundproof - you will hear your neighbors very well. I did not have much chance to interact with other tenants as most people leave in the morning, and come back late in the evening. Also, they were rather quiet. The place was very clean. There is a fully equipped kitchen, and a large living room (I have never see anyone using it). This apartment is a block away from the House of Parliament, there are some restaurants in the vicinity, and a few bus stops some 3 minutes walk away. It takes some 7-8 minutes walk to get to the stop of the famous tram 28. The nearest Metro station will be some 20 minutes away by walk or a few minutes by bus. The hosts are kind and responsive. All in all, a great value. Albeit, if you are coming for a honeymoon looking for luxury and privacy - perhaps look elsewhere.
PS. When in Lisbon, do yourself a favor and buy a Viva Viagem 24-hour pass for 6.30 euro and use it on busses, trams (including Tram 28) and Metro. A single ride on the Santa Justa Elevator is over 5 euro, and Viva Viagem covers it. This pass is a steal.