I just visited Lisbon last week, and I was able to book this Guest House only one day in advance prior to my trip. I will make sure I will cover all main aspects in this review in order to help future guests:
Location: Maybe one of the best selling points, the Guest House is quite central, the area is close to gardens, supermarket and you can commute anywhere as it is 2 mins away from the metro and bus stops.
Cleaning: The room was impeccably cleaned when I arrive. Also, the common areas, such as the bathroom and kitchen were cleaned daily.
Room: The room has everything you need, a double-size bed, a desk to work, a heater and they supply toilet paper and bath towels. The major issue, that I believe can be a deal-breaker, is that the walls are paper-thin. You can hear everything, from listening to the neighbour's phone conversation, to waking up with sirens and traffic noise. Besides the privacy issue, if you are a light sleeper, like me, it can be difficult to have a good night of sleep. Also, the door locks are a bit jammed.
Kitchen and Bathroom: The bathroom has 2 showers with good streaming hot water. The Kitchen is fully equipped, with 1 microwave, 1 small oven and all the other necessary appliances (mugs, cups, plates...)
Price/quality: For Lisbon current standards, I believe it's a fair price. If it wasn't for the lack of acoustic insulation, I would give it 5*.