I recently spent a week in Rosa's apartment with my parents and we loved our stay. The flat was exactly as shown in the pictures, but even better. It was immaculately clean and tidy, yet very homely. The kitchen has everything you could need, and Rosa had left some fruit, wine, and coffee for us. The location is ideally situated for everything; a bakery, supermarkets, and lovely (cheap!) tapas bars can all be found just outside the building; 20 minutes stroll to Las Ramblas; Montjuic a short funicular ride away; out the flat and left is the harbour and beaches, turn right and you find Plaza España (with the 'magic fountain' - highly recommended for a free evenings entertainment). My mother has difficulty with her knees so we were pleased to find a lift up to the 4th floor to get to the flat. There are also two metro stations within 5 minutes walking up or down the road, perfect for going further afield, or even just to Las Ramblas or El Gotic quarter if you fancy a break from walking (3 / 5 stops away). The flat is quiet at night and the beds are comfortable so you're assured a good night's sleep, and the building is serviced by a friendly caretaker who greets you as you come and go throughout the day.
Rosa was very friendly and welcoming, and communications before booking and during our stay were extremely prompt. Rosa was very personable and she even checked that we got back home ok. She gave us lots of useful information for our stay, and even left numbers for a taxi company so we could book our taxi on the last day - booking can be done online for those that don't speak Spanish which I thought was a useful touch.
All in all it was a pleasure booking with Rosa and staying in her flat. For the cost of our week compared to what would have been on offer if we had booked a hotel, we are unanimous in our opinion that this really made our stay in Barcelona. I couldn't recommend her more :)