Our stay here over Christmas was fantastic. The flat was immaculate and incredibly spacious in a modern apartment building complete with access to a gym and roof terrace. The Kukun team were friendly and always willing to help where they could, even over the Christmas period. You'll need to walk at least half an hour (or take a taxi) to access any of the tourist sites from this accommodation, but it is helpfully located between all of the key sites and also close to a metro station and lots of places for food, so this isn't really any kind of problem and would be expected in a city as large as Mexico City.
Overall a fantastic stay in a lovely flat with all the amenities, we would definitely recommend to anyone wanting their own space and staying for more than a couple of days in the city who doesn't want to be right in the centre of the old town.