Though I only stayed for one night, Sevi's place was great. He was very welcoming and hospitable.
My only complaint about the location that was a bit odd was that the toilet was outside the apartment - but that is just how the buildings were built back in the day.
The room I was in was very comfortable. I stayed on a Friday night, so night life was alive and well, but I am a heavy sleeper and the bed was so comfy that the noise didn't bother me at all. Would definitely recommend this place! Especially for a quick trip through Zurich.