I personally had to cancel the trip, so this is the report of my friends who stayed in the apartment:
"The apartment's location is excellent, and it was very clean, neat. Also, the kitchen was well-equipped, so we could even make coffee and tea for ourselves. As it was described we had to climb quite some stairs to get to the apt, which could have caused problems with an elderly person or with a heavy suitcase.
However, the beds (except for the double bed in the sleeping room) were very uncomfortable. The one in the study was so unfit, even for one person, that on the second night we rather moved the mattress to the floor. The bed in the living room was somewhat better, but it would have been hardly manageable to serve two persons.(Maybe would be good for two kids, but definitely not two adults.) "