I think that review of apartment highly depends on context - so here is mine: I stayed in Madrid for couple of days to work from the apartment and to see the city in the late afternoons / evenings
The thing that is clearly positive about this apartment is location - it is next to Puerta del Sol which is in the centre of the city (and there is "Sol" metro station there if you need to travel further using public transport - Madrid has very good metro infrastructure) and for that location it is also fairly not expensive in comparison of other apartments in this area. I really liked that since I had fairly limited time to see stuff in Mardid - so good location was important for me
I like the fact that washing powder and fabric softener was provided in apartment (I was doing trip of 5 cities and it was the only one place when both was provided - in most of the others there were no fabric softener, and sometimes even not washing powder)
Also there are two separate air conditioners - so if you need you can setup to different temperatures for living room and bedroom
On the other hand - during the day i needed to work - and there are couple of things in this apartment that will not make it good place for that:
The most important one was the internet - it was very bad - i was loosing connection often - unfortunately owner was not answering my messages about that problem. I had "back up" mobile internet with me - but because of the location of the apartment - mobile reception was very bad there so it was not possible to work using it.
This is so called "interior" apartment which is quite popular in spain - which mean that all the windows were pointing to internal very very small "technical" patio - and this is resulting with basically zero natural sun light in the apartment during the day which basically draining your energy very fast. If you use apartment only for sleeping and then you are all day long outside - this is not a problem at all (and actually it can help to have full night sleep) - but if you need to stay longer inside the apartment (like me - because of work) - it is terrible experience.
To summarise - i think it is nice apartment to stay if you are just visiting city and want not very expensive place in the city centre that you will be using just for sleeping. But if you are planning to work from it - I think it is not good