The best thing about this place is the location, a perfect starting point to visit all of Madrid's city centre. Although the window faces the street, it's not noisy at all because there is a double window.
The flat is quite small (a bedroom and a living room area with a sofa bed, kitchen facilities and a table), but if you're going to Madrid to visit the city you will use it just to sleep and it's perfectly fine. We were 4 friends (2 couples), two of us sleeping in the bedrooom and two in the sofa bed in the living room and we didn't have any problems.