It was a pleasure staying at Marta's apartment, very clean and cosy - exactly as per photos. Don't be fooled by the entry - it is a very modern apartment which is worth the price and will keep you cool on a hot day. Marta herself is really friendly and helpful, a really lovely lady! She provided us with a map and gave us tips on where to go/visit. She also showed us where the extra linen/toilet paper/towels were in the apartment if we needed it.
The bed was really comfy (in Spain this is not something you should take for granted, some hotels I stayed at had shocking spring - read OLD & noisy - beds!) and it was nice to also have a couch and dining area. The bathroom was a good size - ample cupboard space for my products and I loved the sink! You may notice that the shower doesn't drain very well at the start - it eventually does after a few minutes, just needs to warm up at the start! :-) There isn't an exhaust fan in the toilet but there is a window :-) Not a big deal, I got used to it.
There is a washing machine if you need to get your laundry done - ample hanging space in the outdoor area, my clothes dried in a jiffy! The kitchen was good - more than enough to get by.
The area was good for me - I saw other areas of Madrid which I missed in my last trip. The apartment is not in the middle of the city but it did not take long to walk there (20 mins stroll in medium height heels!). Eitherway you can take the metro in and there is plenty to see around the area (parks, etc). Atocha train station and NH nacional is a short stroll away if you're thinking of hiring a car (book online to collect at one of those places, Thrifty is the cheapest - serviced by Hertz at NH).
If you do visit, be sure to look up Gau Cafe which is a rooftop bar nearby - delicious mojitos!! There is also a Carrefour supermarket nearby if you need to pick up snacks, cereal, essentials etc.The cafes up the street are also nice for a morning coffee or mid arvo drinks.
I have no hesitations in booking Marta's apartment again if I ever return to Madrid.