Excellent location for exploring the main sights in Barcelona! You can easily walk or take the subway to many of the places you'd want to see. We were also given lots of great recommendations from the host, and that was a nice personal touch.
The apartment is spacious and I really appreciated the coffee and snacks we had available to us. We made our own breakfast every morning and all of the cooking utensils were supplied, no problem. Everything worked as expected!
As others have mentioned, you can hear the rumbling of the subway from the apartment. But I think that is common in that area/for a place so close to the subway.