The apartment is clean and spacious, and the location is central, not far from any of Barcelona's spots. There's a parking lot right below the building for those who have a car. Overall, it's a good place to stay if you are looking for a central location, with some living/dining room space to gather in, and you're not worried about maximum luxury.
The furniture in the living room is a bit old (as seen in some other comments), but that's not really an issue.
There are shades over the balcony which makes it nice in the morning and afternoon.
It's great to have air conditioning in the living room, main bedroom, and in the secondary sleeping area (in the corridor but not in the two rooms individually), but you must be careful when making them all work together, plus some kitchen appliance such as the cooktop or microwave: The electrical panel is not cut for this much power and will trip.
The internet router is located in the bedroom farthest from the living room, so there's no real wifi usable in the living room (the signal is not strong enough) - unless you bring a wifi repeater.
Caution: There's no phonic isolation, you will hear the street noise in the morning, so maybe bring some earplugs if you are planning on sleeping in :)