Pros: Nacho is an excellent host and his place is great. All furniture, appliances, and sheets/towels are top notch! The flat is in a vibrant area as well, full of shops, restaurants, and bars. We found it extremely easy to get to and from anywhere in the city.
Cons: Nacho's place was so lovely, I hate to admit this, but it was rather noisy. Now, if you plan on being out super late, you likely won't notice it much in your sangria/beer/cocktail haze. However, if you're looking for a quiet, serene spot to relax during the day or in the early evening, the family upstairs is going to give you a run for your money. It seemed like bedtime was around 11-11:30pm, but again, you're in Madrid for crying out loud and shouldn't get home until 2am or later anyway!