We stayed at this apartment for 2 1/2 weeks. The first thing you notice is the kitchen. You have everything you need! Dishwasher, washer/dryer, microwave, full-size refrigerator/freezer, and plenty of dishes and pots and pans. The bedroom has a small closet area which was perfect to store our luggage. The bed was comfortable for the two of us. The bathroom was a nice size, and everything worked well.
The location is absolutely fantastic! You are less than a half a block from Plaza Mayor, which is one of the central hubs of the old city. You are less than a five minute walk from Puerta de Sol, which IS the center of the tourist area. There are too many restaurants and bars in the area to mention, but we also found supermarkets, fully equipped gyms, and pharmacies. Puerta de Sol also serves as a transportation hub, making it easy to get around Madrid on public transport.
After walking around the area, and seeing the hordes of people, we started to worry that the apartment would be loud at night. Thankfully, it is an internal apartment, and is extremely quiet at night!
To answer the question, would we stay there again? The answer is an emphatic Yes!