This place is really great and I can only recommend to stay there! Contact with Marie and Markus worked perfectly (in English, Spanish and even German), and it was nice to know that there's always someone available during the day in the office in the same building.
The appartement is pretty nice and has everything you need, a good bed, a great bathroom, a well equipped kitchen, everything tidy and clean. The window in the bedroom is facing Calle Feria, it has sun during the day so the small balcony is especially nice to enjoy the weather and watch people. Heating is also working good (what was really important as it was quite cold during our stay in February).
The area itself is just perfect, you have everything around you need, bars, cafés, shops, everything. You can walk into the city center within max. 10 minutes. It's not over-run by tourists, but you still have bars where you meet only locals, and the whole atmosphere is great - I really wish I could live there. Regarding the location it's rather quiet, but if you can't stand any noise during the night (especially on weekends) this might not be the right place for you. But I didn't have any problems with sleeping at all and I would always stay here again.