The host is super nice and helpful. The location is very good: one can easily walk to many interesting museums, great restaurants, vibrant streets. The apartment is as spacious and clean as the pictures show it to be. The doorman is friendly, and the building felt very safe. You are really in the heart of the historic center of Mexico City, in the middle of the action.
There are two drawbacks, though. First, the mattresses are extremely hard and small. Some people love it that way, and they will be happy. For my wife and me, it was painful.
Second, it is very noisy. You must bring ear plugs with you. It is located on a major throughway, and trucks rumble by non-stop, all night long. On Friday and Saturday, in addition, the place just in front has a live band playing until around 4AM, and it is loud. Fortunately, we brought good ear plus and it was doable with those. Nonetheless, if you are the type who cannot deal with noise at all, this is not the place for you.