I stayed at Marina's for 1 month during which I was getting to know Madrid and working online Mon-to-Fri for a company in Argentina.
Marina's place is excellent for either teleworkers like me or students, and I can not recommend it enough.
Rooms are comfortable and quiet. Internet speed is lightning fast. The kitchen has everything. Every guest gets a big space in the fridge and another in the cupboard for all their needs. Bathrooms are clean and there is more than one so that guests don't have to wait. My bed was super comfortable, I got two towels.
Markets nearby are good enough for any daily need and transport to the city is very fast considering the distance (40 minutes to an hour)
Marina's family is lovely. I felt like one more sharing breakfasts and chats and some tv time after work. I know I made new friends in Madrid :)
All in all its a great place and I have not one negative thing to say for the whole month. I definitely recommended and would stay again. 12 out of 10!