The apartment was very nice and cozy, and just as it looks in the pictures. The location is very good, with lots of retaurants, shops and sights within a short walking distance. It is also easy to reach both from the main railway station (we walked maybe 15-20 minutes but public transport would also habe been a good option) and from the airport via the subway, as there is a station a few blocks away. The area is quite bustling but as the apartment is not on a main street it was still quiet enough for an early night's sleep as well.
Communication with Sorin was fast and totally smooth. Check-in was also very easy - although the keybox service's SMS apparently didn't get through to my phone, we got our keys immediately when we got to the key pick-up location, as Sorin organized beforehand for the keybox to be opened remotely once we were there.
The apartment can be a bit cool in springtime (we visited in late March) but the electric heaters provided worked well and warmed up the living area to a comfortable level in a short time. Only the bathroom was somewhat cooler than the rest of the apartment, but not too much. Also, the kitchen has a fridge and a stove, and was stocked well enough with cooking and eating utensils for simple cooking, if one doesn't want to just eat out all the time.
The only thing that could be a major shortcoming for some people is that the apartment is located on the second floor of a historic building, with relatively narrow stairs and no elevator.
All in all a very nice apartment especially for a couple, at a very reasonable price, and located perfectly for exploring the city.