Mar's apartment is a great place to stay in Barcelona and you'll love it. It's a great combination of location, size, amenities, and value. The view of La Sagrada Familia is outstanding. The metro is a block away and you can be to almost anywhere in the city in 15 minutes.
Our family is two adults and four kids and the space was just the right fit for us. The apartment would probably be ok for four adults, but too small for six adults.
The kitchen was well equipped for basic cooking. We prepared breakfast every day and a couple dinners. The only catch is you need to bring/buy any salt, pepper, sugar, spices, etc. that you need.
The washing machine worked well, but it was a little confusing to use. Resetting it to zero seemed to work when it wouldn't do anything. Also, there is no dryer, but there are hanging lines outside the window.
One minor drawback was the water heater is small and takes longer than you would expect to heat. It's also VERY HOT. Be careful not to scald yourself and take short showers, and it will be fine.
We had a great stay here, and we would definitely stay here again.
Highly recommended!