Our group of three adults stayed here for five nights and were very happy with it.
Getting to the flat was quick and easy, with one person taking a taxi from BCN in about 25 minutes, and a couple taking the metro from Sants station 3 stops and then walking 5 minutes.
The neighborhood seemed safe and calm, and it has many restaurants within 10 minutes walk. There is a small supermarket 5 minutes walk away, and two bigger ones are reached in < 10 minutes. You can also shop at Mercat Sant Antoni, which is less than 15 minutes.
The flat is nicely designed and furnished, so you feel like you are in Spain, not an Ikea catalog. All the furniture and beds were very comfortable.
The bedrooms get very dark and are very quiet, so we slept very well. Showers worked great with plenty of hot water.
The kitchen is stocked with a good variety of tools and pots for basic meals.
Two things to be aware of: the wifi signal is currently great in the front room and dinner table (we measured 50mb down/75mb up, more than fast enough for video calls and streaming), but poor or absent from the bedrooms and terrace (the test failed to complete the first time, the second test was 3mb down/1.5mb up).
Also, the flat was stocked with soaps and cleaning supplies, but nothing in terms of cooking ingredients.
The host company was very responsive to my messages, and both the person I worked with in advance and the one who met us for check-in spoke English well, so communication was very good.