My girlfriend and I stayed at Marga's apartment for 3 nights in February. Having gotten into contact with both Marga as well as her assistant Daniel, we were given instructions on how to get to the apartment using the various transport options Madrid has, however they were all very clear. The location of the apartment is great for those that want to be within walking distance of most of the main tourist attractions in Madrid, and for those further afield, the apartment is 100m or so from both a metro stop and a cercanía station.
Within the apartment, it looked exactly as the photos suggested. The design made it feel very cosy, especially when the temperature dropped outside.
All 3 of the balconies opened out on to the street you enter the building from, 2 being open air and 1 with windows. These were great to open with breakfast and dinner, although later in the night it can be louder there are earplugs if it's too loud, and in the colder months it does seem as though a lot of the heat escapes through these balconies.
In all, we very much enjoyed staying in this apartment and if we were to visit Madrid again, I will be sure to check if this place is available first!