Highly recommended, especially for a couple.
My wife and me stayed here a month from December 2019 to January 2020 and absolutely loved it. We felt like it was our home. It is very nice, roomy and well equipped, including clothes washer and dryer, which is quite unusual in such apartments; this saves time, money and hassle. The kitchen is also very well equipped though the stove is electric, and we are used to gas. The bed is great and it feels good to have all the apartment space around. The A/C works well and the bathroom is quite big and comfortable, with a truly usable shower.
The location is hard to beat: with two main subway lines and two bus stops less than half a block away, and the Sants train station about four blocks away. It allowed us to get to and from the Sants train station by foot even carrying heavy luggage. On top of that, it is a block away from the Sants market, where you get high quality raw and cooked food and in which there is also a Mercadona high-value supermarket, so you get the best of both worlds, and within walking distance of many other supermarkets (Carrefour, etc.), cafeterias, restaurants, bakeries, pharmacies, gift stores, hardware stores, etc.
The only cons are the view since it is at the same level as the Sants square in front of it, and that there is no elevator at the apartment level, so you have to go one floor up and down the stairs (neither was not an issue for us).
Finally, Carmen is a great host. She was always reachable via phone or WhatsApp. She discovered on the day of our arrival that the water heater was leaking causing the differential breaker to trip, and managed to get a new one installed in two working days.
Summing up, we recommend it and would definitely stay again if it is available next time we visit Barcelona.