We were a group of 7 - 2 grandparents, 2 parents, and 3 kids. The apartment is huge and there was more than enough room for us all. It's a beautiful older building with plenty of architectural detail - including gorgeous ceilings! The furnishings were attractive IKEA pieces, including the mattresses which were fine although perhaps not the best super-high quality. The kitchen is completely outfitted but it seems like nobody has ever cooked in it - there were no spices or oils left behind by prior tenants, so if you do plan to cook here you should plan to bring those with you. There was also not much in the way of toiletries, although each bathroom had a hair dryer and tons of toilet paper. Plenty of towels, but no bath mats so just sacrifice a hand towel. (Note to Anericans: wash cloths are almost never used in Spain, so if you want one, bring your own.) We heard no noise at all from the neighbors, but there is quite a lot of street noise in the front bedrooms (the ones with queen size beds).
Dani and Alex were wonderful and could not have been more accommodating. They were easy-going about all the arrangements and responsive to all our questions and always answered the phone. We weren't sure how to work the heat so Alex came back to show us. They let us do late checkout since nobody was coming directly after us. Great hosts!