I don't know if it is always like this, but our experience in Mathia's place was a bit of a mixed one. Starting with the positive things, the apartment is very well located, really a 10-minute walk from the centre of Copenhagen (where you'll find Tivoli, the Food Hall, the shopping street, a supermarket etc). It is also a very quiet building, we heard no noise at all from the neighbors.
But there were a few problems. Mathia's sister was supposed to meet us in person to hand us the key to the place. But as we landed in Copenhagen we got a message from him telling us that she wouldn't be able to show up and that we had to go pick up the keys somewhere else. That is always something we find a little stressful to do because as travellers we were tired from the flight, didn't know the city and had bags with us. Mathias gave us the address and we first tried going up there in a cab. But it turned out to be the wrong place (!).
We were very glad to have Internet access with us because we were able to contact him again. He then gave us the right address - a 10-minute walk from his apartment - and my wife stayed behind with the bags on the street, as I went down to get the keys. So that was that.
The apartment is simple but comfortable, but there were no towels (we asked for some and several hours passed before a single medium-sized towel appeared wrapped around our door knob (!)). I would recommend bringing sleeping masks because there are no blackout curtains. Especially in the summer, when it doesn't really get dark and the morning comes at around 4 a.m.
Mathia wanted to meet us in person on our check-out day so we could give him back the keys. We settled on a time and...he didn't show up. We sent him a message and only then he told us he would not be able to come.
Oh well...