I stayed in Raúl’s apartment for a month (October 2019) in connection with a longer visit at the Complutense University. All in all, my stay in the apartment went well, but there were also a few things which bothered me a bit. Summarising my experience, I would say that the apartment is probably well-suited for shorter stays where the location is the top priority, whereas the value-for-money is not amazing for longer stays (at the time of my booking, it cost 1.875 EUR for one month).
I didn’t have any serious problems during my stay (e.g. the washing machine, stove, water supply etc. worked just fine), but as a long-staying guest you had the sensation of getting too many disadvantages from staying in someone’s home (personal items taking up space and warranting care), whereas you didn’t really get many of the benefits (updated, well-functioning fixtures). I also found the place to be sparse on lighting, especially in the bathroom where only a single desktop lamp was mounted at the wall.
For the most part, I found communication with Raúl to be quick and rather friendly. He was also very welcoming when I asked about the possibility of having a friend come visit me. At other times, however, I found his attitude a bit patronising - for instance, on one occasion he commented that I had set the temperature of the radiators too high and re-adjusted it himself, even though 1) the central thermostat had a defect which forced you to slightly over-set it, and 2) the setting of the temperature should clearly (within reasonable bounds) be the decision of the paying guest.
In conclusion, I would say there is some room for improvement, but, as I said, some of my issues were related to staying there for a longer period of time - also, Raúl told me that he would make improvements for the future, e.g. with regards to lighting.
Again, the location was really quite extraordinary, in particular for going out to restaurants and bars in the evening, and - despite of being located very centrally - the apartment was quiet, even during the nighttime.