First of all - the girls could be running in a competition for the nicest hosts on Airbnb. Seriously. Communication with them and the welcoming at the arrival was top notch! Actually we didn't see each other ever after as the guest part of the apartment is seperated from the hosts' part.
What I also liked was the breakfast which was simple but nicely prepared every morning and waiting for you on the kitchen table (typical sweet Spanish desayuno - coffee, juice, milk, toasts, cupcakes, etc). However, there is no kettle in the kitchen so if you want to make a tea or you just need hot water for anything you need to use microwave to boil it (yep, seriously). Also it was quite a challenge to find a rubbish bin in the kitchen... (good luck with that!).
What was disappointing in the room itself was that it lacked any window curtain. There are curtains on the pictures and they would really make the room more cosy. The other problem was that there was no any small lamp in the room. The only source of light was the big main lamp at the ceiling. So having no curtains you had two options - stay in the dark or to be in full light with everybody outside seeing you in the room. If you wanted to read anything in bed you had to be doing it in the full light, then to turn it off you needed to go to the corridor where the switch is located and go back to bed in full darkness. So the room felt very cold and not comfortable - it basically only has a bed, two nightstands and a tv-set on the wall. Nothing more.
The best part of the room was the private bathroom. But - on the pictures you see a bath with jacuzzi. The problem is there is no way to use it as there is no plag to keep the water in the bath. So you basically only have a shower.
You also have a gym and a swimming pool which I didn't have a chance to try because it was very cold in Madrid these days.
As for the location of the apartment - it's very convenient. Yes, you always need to take a metro to go anywhere but you have it just across the street and can get anywhere with the maximum of one change of metro-lines.
All in all I was a bit disappointed with the stay especially with the room and no kettle in the kitchen. You could expect more for that money.