Our stay was fantastic. I'll cover a few practicalities first.
Armando was very helpful while booking and during our stay, though it was Pau who showed us around the apartment as Armando was not available on the day we arrived. He was also very friendly and helpful and told us everything we needed to know.
There is A/C in the apartment, only in the main living area but this, combined with the ceiling fans in each room, made it very easy to create a fresh atmosphere even when it was hot and humid outdoors. But of course, there's always the option of opening the screen doors and letting a breeze in. You may just hear a musical concert from the square below!
The newer screen doors/windows block out almost all street noise. You will quietly hear the bells of La Sagrada Familia in the daytime or maybe the occasional siren, but the noise of people talking and moving about the street below is completely blocked. Also the street gets quieter at night as the nearby bars are a block or two away. Some sound does carry over from the neighbouring apartments so you may hear them talking, but the neighbours are very amicable so you shouldn't have any problems.
Added to that, it's an extremely well-appointed and clean apartment with plenty of space and everything you need to have an enjoyable stay.
The location is excellent, on the street below you will find a selection of good restaurants, bakeries, gelaterias, a large souvenir shop and others. There is a metro station at the end of the street which makes it very easy to get about the city.
But of course no review would be complete without talking about the view. Your balcony will look directly at La Sagrada Familia, and over the park in front of it. It is quite simply the best view you will get of the building, much better than simply being stood at street level in front of it. While it is a narrow balcony, it is possible to squeeze the chairs in so that you can have a drink while looking at the building, which is incredible also when lit up at night. Just be sure that if you do this you don't leave the room light on or make too much noise as there are people living adjacent who of course have to go to work and have their daily lives.
All in all it was an incredible and memorable stay which allowed us to see the best Barcelona has to offer. Thanks!