I invested alot of thinking in what to write, because I had a very bad experience in renting this apartment, but I hate to spoil someone's income.
From only 2 hours after I made the reservation (1 minute after receiving Maria's answer regarding the 3rd floor without an elevator) I tried everything I can to cancel it but they refused.
We came to Barcelona for 7 nights, with 3 kids, one is a 6 months old baby and this apartment is absolutely not suitable for families like ours.
Not only it is on the 3rd floor without an elevator, but the stairs are very old and broken. It was extremely hard to return every night and take everything up, including the baby and the stroller! There is also some problem with the door lock so we had to "fight" it... unfortunately, Maria or Vincent never bothered to update us about this problem, only when we asked after a few days!
The overall communication experience was bad ( I asked at the last day where to leave the keys when leaving at *noon*, they replied "you need to checkout before 12"...).
In general, there are good things in the apartment such as the nice kitchen and good warm water in the shower but I think that the base of Airbnb is social and service/hospitality is the main character a host needs and they lack of it! Sadly, I do not recommend renting an apartment from them.