Positive:
Location great, the apartment was clean.
Negative:
The floor inside the apartment 501 has an obvious inclination (!), which is challenging for people with kinetic issues. Not to mention that you constantly feel dizzy while walking from the first room to the second via the hallway that connects the rooms, because of the floor's inclination. The floor in that apartment is definitely not flat, I don't know why. We did not bother to report this, however, because we were out all the time.
Also, there were some visible cracks on the walls above the entrances to the kitchen and the hall, but that was not a problem to us. Generally, the building is very old (the elevator small etc) but again it was not a problem.
Finally, we scheduled a cleaning service (they gave it to us for free, as a reward of sorts for staying a week) but no one ever came to clean up the apartment or change the towels. :(