We stayed five days in CDMX and the apartment was a great base for our exploring. I like to "stay local" and this was great because of the location - close to many things (only a 10 minute Uber to Zocalo, Reforma, Roma, Chapultec, etc (not to mention that the Metro is only a short walk away and got us everywhere for 5 pesos for a local vibe), yet we were away from the noise and bustle of the downtown.
There is a doorman 24x7, so we felt super safe and also welcomed each time we returned from our adventures, or even going down the block to eat at one of the local restaurants. (BTW - Tacos de Carbon Los Jaroschos is only 50 meters away, we stopped there for tacos every day and got the best service!).
The apartment was comfortable, the king sized bed was just what we needed to collapse into each night with warm blankets (no heater and it gets cold at night in Mexico City!), soft pillow and a sleep inducing mattress. We used the kitchen for breakfast daily (the OXXO on the corner has everything we needed) and even had coffee up on the roof (nice table and chairs just for enjoying the morning).
Perhaps best of all was the service - whatever we needed, we asked for and promptly it showed up. More bottled water? Here they are! Fresh towels? Here you go! Room service? On it!
I highly recommend staying at OM, a great place and a very affordable price.