Thanks for posting a link to my site, Nathan! I've been to the Mercado de Sabores Poblanos several times, and the quality of food is equal to what you'll find in many fondas and more traditional markets/street stalls around the city.
Basically, the city government moved all of the "prepared food" vendors from an older market across the street to the new market. I believe that the idea was to provide a place that tourists worried about hygiene might feel more comfortable eating. The new market also allows you to try many different regional dishes in one location, which is a bonus if you're pressed for time. (Its vendors are essentially the same as those you'll find in more traditional places.) That said, some visitors complain that the new market's atmosphere is too sterile or like an airport food court and prefer the older ones, such as Mercado del Carmen and Mercado de la Acocota. (My personal favorite is the main market in nearby San Pedro Cholula.)
Wherever you decide to eat in Puebla, it's hard to go wrong, as long as you choose stands and items that look appetizing to you. Buen provecho! ~Rebecca