This is a really cute little studio in the heart of Alfama (historic district). The location is ideal: you are steps away from the 28 and 12 tram lines (they actually pass it front of the building), very close to the stunning views of the Portas do Sol, surrounded by small restaurants and bars.
The studio itself is small, but decorated with taste, and extremely functional (washing machine in the studio, IH range, fast wifi, pots, pans, silverware, you won't need anything). The main bed is comfortable (I didn't try the sofa bed). Everything was renovated very recently and the amenities are essentially brand new. There are many power outlets everywhere, which is very convenient.
As a small warning, people with limited mobility need to know the studio is on the third floor of a traditional building, which means no elevator. But then again, people with limited mobility may want to consider other neighborhoods rather than staying in Alfama (cobblestones everywhere, and very hilly).
Note that, despite the fact that the studio is just under the building roof, many small windows allow you to cool it down quite quickly in the evening.
In a nutshell, the place is great, and I would definitely stay there again. Ideal for solo travelers or couples.
Travel tip: for breakfast, I do recommend pasteis de nata from Pastelaria Alfama Doce, within walking distance (3-5 minutes or so). They're cheap (much cheaper than what you get in Baixa or Bairro Alto) and delicious. The little workout you get walking around Alfama can be used as an excuse to indulge even more!