Nothing is lacking in this clean and well decorated apartment. Whatever flaws exist (sound of neighbouring apartments, spotty wifi) are common to all such older buildings in Madrid.
What sets this place apart from any other accommodation I can think of in the city is the location, which is beyond perfect. A hipster food hall/market is directly opposite, containing a supermarket, and a panoply of cafés, bars, restaurants and shops surround the apartment in all directions. Despite the abundant street life, bedrooms are at the back and are peaceful and quiet. Chueca metro station is literally less than a minute’s walk away. (Good luck getting an outside table in the square.)
Gran Via is 5 mins walk away; Prado and Plaza Mayor, 15 mins. You’ll feel a part of local life here, with everything you need on your doorstep.