I've been in Carlos & Victoria apartment for a week end and it has been a great experience. The house is as it is shown in the photos and cleaning was perfect when we arrived there.
Carlos & Victoria are really helpful: detailed email about how to check-in and check out and very useful information about how to get to the house from the airport with differents means of transport. I suggest to use the metro, because is very cheap (6€ single ticket) and it takes less then an hour.
The house is in Lavapies, a central and multi-ethnic neighborhood perfect to move very quickly to different location: Plaza mayor is just 10 minutes walking.
I strongly recommend this apartment to spend a week end in Madrid!