Norma and Javier's apartment is great. It was clean, comfortable, and had lots of nice touches that were super convenient (i.e. coffee, laundry soap, netflix, shower gel/shampoo incase you forget yours).
There was 24/7 front desk staff and security, and all the neighbors seemed like nice, professional types. The neighborhood itself is also very safe, with nice parks and tons of street food in a short walking distance. A very nice subway station (Insurgentes) is a 3 minute walk away and can take you to Chapultepec park, El Zocalo, or the airport for 5 pesos ($0.25).
Norma and Javier themselves were great too, with Javier checking before my flight landed to make sure I understood how to arive at the apartment and all my questions were answered. I didn't have a need to contact them during my stay (because everything was perfect), but I'm sure if I did they would've answered quickly.
A couple small things to keep in mind for people considering booking here.
1. There is no airconditioning. This is standard in Mexico City since the temperature is super comfortable from 60-75 degrees. All the windows can slide open to get a nice breeze though.
2. As a short stay visitor, your not given a code/fingerprint to enter the front door of the building. Instead, you ring the doorbell and an employee of the building will open the two doors necessary to enter in the building. Since someone is available 24/7 this isn't an issue, it's just a little awkward to have to keep calling someone to open doors for you every time you leave the building.
I highly recommend this apartment for anyone traveling to Mexico City. I went alone but the two bathrooms and two bedrooms would make it great for a small group. I hope to be back to Norma and Javier's apartment next time im in CDMX.