The apartment is lovely. It is beautifully designed and is in a great location for exploring Madrid. It has air con which is a necessity in the summer. Maria has great little touches like the breakfast cereal, basics in fridge, gazpacho, milk etc....
It has all the facilities you could need and we absolutely loved the projector for watching movies!
Mylene the cleaner was also fabulous.
The downside is that the apartment location (close to restaurants and bars) means that it is very noisy at night until very late - the early hours of the morning. This makes it very difficult for kids trying to sleep.
Additionally, the upstairs bedroom is not really a bedroom - it is really a sleeping space in a roof attic. The steps are extremely steep and shallow - like a ladder. It is also extremely hot up there. We ended up sleeping on the rather bony sofa bed instead (which really is only big enough for one person).
As a couple, we loved the apartment and would not hesitate to stay again, but not with our little one as the nightlife noise made it it difficult for sleeping.