I stayed for 6 months at Leon's beautiful house. Let me summarize my experience for you:
- Leon: couldn't think of a better host. Very responsive, helpful when something had to be fixed, and extremely friendly. He will also give you tips on things to do, etc. When he was out of town, his mum / friends would take care of any needs.
- Apartment: in case you were wondering... pictures do justice, the apartment is incredible, especially those huge windows in the living room. You won't want to leave, seriously. The terrace was just renovated and is perfect for bbq's. The building is very secure, the guards are extremely nice and will do you favors whenever you need them (keep the keys, etc). Also good to know: the building is earthquake-proof :) Oh, and the huge TV in the main bedroom is a plus.
- Location: also great, right next to an underground station, a secure taxi stop, and less than 5 minutes walk away from the great Chapultepec forest, or 10 minutes from the lively La Condesa. I felt safe walking around the neighborhood even at night (of course this is no guarantee, always be cautious).

Areas for improvement: noise isolation. Not a big deal, but some windows are a bit old and you can hear street noise. Not really a problem at night, as this is a very quiet neighborhood.

So once again: this place is great, don't even think about it if you have a chance to stay here. This is probably the best place to stay at on AirBnb in Mexico City. And of course much better than staying in a boring hotel :)