An excellent place to stay in Barcelona. We were a family of 6 including young children and my ageing parents. We were contacted by Silvia a couple of days before we arrived and were met at the apartment and shown around. Location is very good - metro a few hundred metres away (L5 is the closest and has elevator access). Lots of bus stops nearby to get to various attractions - this is the easiest way to get around I think. You can walk to some of the attractions too if you wish. Large supermarket across the road and local grocer shops (open longer) also close by.
No real road noise in the apartment but as someone else mentioned, the ceiling is thin and you can hear people running around upstairs; but was not a major issue.
There is a small lift in the block - it was small but fine for us (only my mother needed it).
All the rooms are decent sized and have storage space. The room nearest the entrance is next to the stairwell so can get a little noisy in the mornings but didn't cause us any issues. All rooms have an AC/heating unit as does the living area. Living space and dining a reasonable size with a TV too. Extending table in the dining area (but we used it un-extended).
Two showers but we found that if we tried to use both at the same time, then the combi-boiler couldn't cope and you'd end up with luke warm water in both. We just timed it so as not to use both at the same time. Hand and bath towels are supplied.
Kitchen is small but well stocked with pots, pans, plates, cutlery, etc. We made good use of the kitchen to cook breakfast and some evening meals.
There is nowhere to stow luggage on your last day but we used an online service (search Barcelona luggage storage) to store the luggage for a few hours at a local store for not too much money.
Overall, excellent - would recommend the place for families/groups.