This apartment is quite spacious, which was nice with two kids who want to move around a lot.
The location is nice, in that it is within a reasonable walking distance of most of the major sights most people would want to see in Madrid. It was at the bottom of a hill leading up to the city center, so it can be tough walking for kids. The street outside is pretty busy, so it can also be quite noisy at night and you can hear from the neighbors within the building, too.
There were quite a few small issues that we ran into in the apartment. We had to thoroughly clean the coffee maker inside and out before it could be used (it was in very bad condition and missing some parts but we made it functional after some work). A number of other kitchen supplies were also in need of a good cleaning and the wine opener was broken, though my husband was able to fix that, too. When we went to give our kids a bath, we found there was no stopper for the bathtub, just a chain. A number of drawers were difficult to pull out or push in if you needed something from them.
Overall, it was a great amount of space and a good location but lacked a number of details on the inside.