We had a good experience.
It is clear that the apartement is old. Expect a creaky floor, some walloutlets that aren't completely attached to the wall anymore, a loose doorknob...but nothing that would cause much trouble, aside from the lack of hot water and the occasional smell of the sewer from the bathroom.
Overall, it is a very charming place to stay. We really enjoyed our time here, and the view is absolutely wonderful. In no time you're at the heart of the city.
Also, Juan was amazingly kind, and our check in with Joana was very pleasant.
If you're looking for a taste of the historical center of Lisbon, this could be perfect for you!