Stayed here with my wife and her brother last week and whole heartedly agree with all the 5 star reviews.
The apartment is lovely, has everything you need and is very clean. We all agreed it was perfect for our stay. Barcelona is a very busy city so we appreciated being in a quieter area on the outskirts. The Metro (Barcelona's version of the tube) is a 10 minute walk away and will take you anywhere quickly for 2.15 Euros. The taxis are very reasonable too.
There are several supermarkets nearby and Alex showed us the best one which was 5 minutes walk away.
Alex is a great host. He will give you as much help as you want but leaves you to enjoy your stay.
I would have no hesitation in recommending this apartment to anyone looking to stay in Barcelona and this will be my first choice when I return.