Pros: There isn't a better location in Barcelona. I could walk right out the door to get coffee, groceries, gifts, and the Metro. I walked to several Gaudi sites from the apartment. The apartment is clean, bright, and with great views of La Rambla. The managers were extremely helpful and friendly. When my flight was canceled at the last minute, they let me stay an extra night and gave me an excellent rate. They also brought in a chair that I needed for my work. The apartment itself is well-equipped with everything you need in the kitchen, plus a great little washing machine.
Cons: It is not necessarily a cozy place -- not a single rug on all tile floors, not even a bath mat; the shower needed some maintenance; the bathroom light and fan run on the same switch; mattress and pillows are flat and hard; futon couch is awkward to sit on tho handy for an extra guest. If you stay for a long time, the noise from the street might wear at you--an apartment on a higher floor might be quieter. Rambla F is on the third floor. It gets very little sun. Both sinks are hard to use without getting water on the counters. These are little things that got to me after 10 days, but might not bother other people.
You can people-watch to your heart's content from the windows. There is a wonderful old-fashioned elevator. Doors are secure, and you feel very safe in the building. Great little pita kitchen on the ground floor. There is a large grocer a few steps south, but a much friendlier, smaller grocer across La Rambla, down Carrer Canuda. I walked to a guitar concert and to the wonderful restaurant, 4 Gats, and did plenty of Christmas shopping. The apartment is in the middle of a major shopping area, close to the University of Barcelona, and right off Placa Catalunya, which is a Metro hub. It's very easy to get out to the main sites and back again.
Its a lovely place that meets all your basic needs. I would give it three and a half stars if I could do half-stars.