Observations from a month long stay:
First off, this is probably the most ideal location we could have wished for. Beautiful street, in the heart of Eixample. Grocery stores, markets, shops of all kinds and restaurants galore - probably a dozen just on one side of the block. Metro, busses and trains and are all nearby and make it a breeze to get across the city, the airport or even out of town. We went to the beach in Sitges a few times and getting home was simple even when tired, sunburnt and sandy.
The flip side to this wonderful location is that there is street noise, especially on the weekends when people regularly come home at 6-7am. We got used to it by the end of the stay but it was a surprise at the start. Also, don't even think about having a car unless you plan to keep it in a private garage, street parking is almost non-existent and frankly, you don't need one anyway.
The apartment itself is on the 2nd floor a gorgeous period building, with a grand entryway and antique elevator. The apartment is behind a pair of very solid secure doors and you need to be careful not to lock yourself out, as we did once.
Inside, the apartment has tall ceilings and classic tile floors. The kitchen is typically small but functional and houses a washing machine as well as the stove, microwave/convection combo and decent sized fridge (for European standards). The secondary bedroom is smaller, dark and quiet - good for sleeping but not much more. The master bedroom is larger and has doors that open onto a shallow balcony overlooking the street below. It's much brighter (and noisier) but the balcony is well worth the extra noise. The dinning room/living room combo also has doors to the balcony as well as a table and chairs for 4, small couch, coffee table and tv. Wifi is solid and supported multiple video calls concurrently for work. The air conditioning too was solid, making the apartment a nice oasis in the hot afternoons. It did take some time to cool off so we often left it running on low while out to keep the space moderately cool.
Running the AC, microwave and stovetop at the same time we did manage to blow a breaker but that was easily fixed and the lesson was learned.
The place is fitted with Ikea furniture throughout, meaning you will find everything functional but not much more. We did buy a few accessories for the kitchen (spatula, french press etc) as we did a moderate amount of cooking but it was "fine" overall. The couch, as we saw in a review prior to arrival, was not great - however our goal was to spend time in the city so it helped remind us to get up and out!
There is also a roof deck that was gorgeous but very warm during the day as shade was in short supply. Nevertheless it was a perfect place to retire in the evening with a bottle of wine while trying to pick a restaurant for the night.
To sum things up, this was a great apartment in the best location we could have possibly imagined. There are things inside that we would change/update but, being a full time rental unit, they were completely expected.