Our group of 12 stayed here in Madrid for 5 nights. We loved that the Airbnb could comfortably host all of us (everyone had a bed) and the location is perfect for exploring the city and checking out the night life. I'm 6'4", so the slanted attic roofs were definitely difficult to avoid and I hit my head a few times (ouch). However there is one bedroom with tall ceilings, and in the kitchen and that bathroom I had no issues. We really appreciated having 4 bathrooms for all of us.
What may not be obvious from the listing: there are enough rooms for 12, however the walls are very thin. This is only a problem if those in your group want to sleep in while others want to stay up and drink. Our only other complaint is that the WiFi was quite weak; even when 4 people were home it was impossible to watch videos. With 12 people on the Internet I couldn't even check my email.
If I am in Madrid, I would definitely stay here again!