We really enjoyed our stay at this apartment - the location is fantastic and although in Barrio Alto far enough away from the nightlife that you can get a good night's sleep. Super comfy bed and brilliant recommendations from the owners of places to eat and drink.
The apartment is on the 4th floor and up 8 flights of stairs (we didn't mind this - but it could be a challenge for some people), there was a slight smell from the bathroom and kitchen sink but I put this down to the general sewerage system.
We also had a slight issue with the WiFi but as we were using the apartment as a base it wasn't a problem (we were on holiday and wanting to experience the sites and sounds of the city not sit watching TV/Netflix so again not a problem for us) and Juan went out if his way to resolve this for us.
I'd highly recommend a stay here as it's ideally situated and a lovely apartment.