Overall, would rate it 4.5/5, due to incredible value for the money. It was very inexpensive, yet despite that, the location was ideal, and rooms were very clean and newly renovated. It's a small boutique hotel, so you won't have room service, or other big hotel amenities, but I never need that anyways.
My only complaint is that we got a free upgrade to a 'mansard' room (top floor, with sloped ceiling), and while the room may have more square footage, the charming sloped ceiling is quite annoying for anyone sleeping on the left side of the bed. Very easy to hit your head on the ceiling, or on the metal rack attached to it, if you don't duck everytime you walk from the bed to the washroom. So, my advice would be to turn down a mansard room.
That being said, our stay was very pleasant. The room was incredibly quiet, and that is important to me, as I am a light sleeper. The front desk staff were very friendly, and all of them were young and 'hip'. There was a youthful energy, but at the same time, the staff were all very professional, and clearly had been trained well.
Location is fantastic; the bottom of the Santa Justa elevador is right across the street, and all of Rossio, Chiado are at your doorstep, with Baixa and Bairro Alto a short walk. You can walk everywhere, although if you have never been to Lisbon, be ready for all the steep hills ;)