We had a very nice stay at Mirabela's flat. The best thing about the flat was the location. I was a little unsure about the location before we got there but La Barceloneta is a really nice area right by the beach with loads of restaurants, bars and easy access to a metro station to get around to the rest of the city.
As others mentioned it can be a little loud at night but not all the way through the night and truthfully, after the first night this didn't bother us at all and we didn't feel unsafe at any point. We were checked in by a friend of Mirabela who was very friendly and helpful and could be reached if we needed anything. Overall we are very happy with the stay and Barcelona is an amazing city!