The location turned out to be amazing; it's very central to most activities in Barcelona. Conveniently, two metro stations are within walking distance (same line). We didn't have any problems with outside noise, as suggested by other reviews; maybe we were just too tired to notice :) The walk up the stairs was not a problem for us since we are all able and fit but it does require some endurance.
If I had to change anything about my trip: I don't know if I missed this in the description but Palau Güell (museum) is a stone throw from the building so you can include that one for your first day after lunch in La Boqueria. We instead went to park Güell which we should have reserved for much later since it's much further.
The host gave us accurate information, and communication to check in and check out was simple. This made our stay so much more convenient, and we just had to enjoy Barcelona. The furnishing of the apartment was sufficient and modern.