Location was great -- about a 12 minute walk to La Sagrada Familia tourist site and about 1 minute walk to a coffee / pastry / sandwich shop called "365".
The unit itself varied from the photos: 1) the closet was near the entry door, not in the bedroom; 2) there wasn't an additional counter space between the stovetop and the sofa; but neither of these are dealbreakers. My wife and I do wish we had more space on the bathroom sink and kitchen counter, but the pictures are accurate.
Check-in process required the memorization of two numeric codes -- no big deal; and the separate laundry unit with another numeric code was worth it. A huge plus: the check-in time was officially 3pm, but we were able to get in earlier than that.
Flateli Rentals was pretty responsive, usually within the hour during normal daytime operations.
Overall, a good place to stay and we do recommend Flateli Rentals.
Additional note: be sure to send copies of passport if you're a foreigner; as well as pay the tourist tax.