We booked this as a group of four and enjoyed our stay overall.
Positives: location is perfect (50m from metro/furnicular/shops and next to god knows how many restaurants and bars), it's a very high spec apartment (we hired a private chef on two nights and they had no issues in the kitchen), the host responded instantly with suggestions or any requests for help and the general furnishings are to a very high standard.
Negatives: It is very noisy throughout the night due to the neighbouring nightclubs/relatively thin windows and then people in the streets afterwards directly outside making noise. Case in point on over 70% of nights people started playing drums or singing at 3-4am directly outside the bedroom windows. Luckily we were deep sleepers but this is something to bear in mind if you are looking for a quiet stay. The apartment is also at the top of four steep flights of stairs and requires relatively decent fitness to do multiple times a day.
Overall, I'd still stay again given the location and quality of the apartment overall.