Maite’s place was good. Located in Madrid right across from Atocha Station, you can access the metro, or buses to head into the city, and the train if that's your arrival/departure point. Maite recommended the 001 bus which is a free bus that picks up from Atocha, and heads NW toward a lot of the main tourist attractions. The Parque El Retiro was just to the north, and there are a handful of restaurants nearby, (Sep7ima was excellent, and Piazza Castello has a unique mascarpone mousse dessert).
There is a strict check in process, which we were prepared for as it was mentioned in the House Rules, but we almost didn't make it within our 30 minute window because we got lost in the metro and had to head street-side to hop in a taxi instead. If you're arriving from the airport, or Chamartin station, make sure you plan out your route well and account for enough time.
Maite went over everything when we arrived. The room was clean and simple, though quite small. The bathroom is shared with the other rooms, not really a big issue, you'll hear when it's in use with the squeaky door and creaky floors. The bed is fairly firm, so if you need a soft mattress, you might not be satisfied. During our check-in we were informed that there wasn't AC (despite that being listed under the amenities), but that we could open the window in the room to let the cool evening air in. While this was ok for keeping the room cool, there isn't a ton of airflow as the window opens to the small central courtyard, and no fan in the room to circulate the air either. It also posed one giant problem, the cacophony of noise. Each night of our stay it was quite loud from the other residents of the apartment complex until around 2-3am with a combination of conversations, arguments, music, televisions, and on our final night a house party 4-5 floors up. We tried to use a white noise track and earplugs to drown it out, but to no avail. Closing the window only helped abate the noise slightly, and then it was way too warm in the room. Therefore I would warn, if you're a light sleeper/need it cool in the room, this probably won't work for you.