If you want to stay in the historical center (which I would recommend for a first-time visit), this is the place. You're within walking distance of many things to see and metro stops and the area has a new crop of great restaurants. We were always assisted quickly by Gonzalo's friend Ezequiel, who greeted us at the door upon arrival and saw us out. We arrived early; the apartment was still being cleaned but we were able to leave our bags--she did a great job and made sure we had what we needed. Gonzalo responded quickly to every question. Also, the apartment has a water purification system so you don't need a garrafon! The building is very secure.
A few tips to get the right start to your stay: The pool is great--heated!--but you *must* have a swim cap *and* flip-flops or other type of water shoes (they'll call them chanclitas). Security will not let you into the pool area without them (or they'll threaten to fine the apartment owner 2,000 pesos). Goggles are also supposedly required; no one wears them and I didn't have any, but I'd pack them in case (they don't sell them at the little store). The water heater will be a problem for some--i.e., those who don't live in Mexico and are not accustomed to having to light a pilot. During the rainy season, it goes out a lot due to the wind and being on a high floor. Ezequiel told me they are buying a new electric one soon, so this may not be an issue.
Overall, you'll have a very comfortable stay in a central location!