I stayed in Marks appartment with two friends. The beds were comfortable and we had enough room. All of the necessities were there.
Mark was very helpful, had good tips for places to eat etc. If Marks wasn't available his employees were also a great help. The quarter is nice. Not too oturisty but definitely in walking distance to all the important sights. Although there's a tram right in front of the door, if you would prefer to take public transport.
You can't hear the street noises at night which is great.
Two things of note though. The art in the appartment has changed from the ones you see in the photos. Some of the new art can be seen as explicit. I personally found it really cool and like it but I imagine family with children might not be too pleased about it.
The bathroom is as someone else has already said quite rock'n'roll which means the bathroom door is a curtain and not an actual door.