The apartment is bright, spacious, well-equipped and comfortable for a family stay in the city. We had a great time, and would recommend it highly. It's in the grid section of Barcelona, a lovely neighborhood with turn-of-the-20th century buildings and streets shaded by sycamore trees. The apartment is on the top floor (with elevator), and has terraces with a charming view of the square in the morning. It has the feel of classic Baracelona (building across the street says 1904) but none of the tourist mobs that are always present in the Gothic Quarter in July. It's a short walk to two Gaudi houses on Passeig de Gracia, and about 25 minutes walk from the top of La Rambla. It's also easy to take the V13 bus to and from the tourist section. A good bakery (Turris, one block southeast) and supermarket (Bonpreu on Carrer de Provença, three blocks southeast).
Buying individual bus tickets is strangely difficult in Barcelona, as is understanding the system (e.g. are bus-bus transfers allowed with a single-trip ticket? We never figured that out.) Tourists are strongly nudged toward buying multi-day transit passes for about 8 euro per day. Three rides and you almost break even; four and you save. Having mobile data on your phone is super helpful -- google map directions will tell you what bus combination to take from anywhere to anywhere.