I definitely disagree and wish it were back at Union. It did very well there, I enjoyed it tremendously, and obviously many people did with how busy it was--very convenient to actually have good food options right at union. I went there a few times a week either when travelling myself or meeting a friend coming into/heading out of the city.
Once the Union food court opens, and there are more food options, I'd agree that it's probably not necessary to have this out front. Mind you, "necessary" and "good" are not the same thing, I think it's a very nice space that added a lot to the station by having an outdoor patio area, but with a food court inside I wouldn't beleaguer that point. But before that, I definitely don't see any reason to get rid of it. The few current tenants in the York concourse have fairly minimal food options between them, and virtually nothing constituting an actual lunch, which many of the market tenants did have.
In terms of pedestrian flow, a LOT of Union users use the direct below-street access between the main station and the TTC/main PATH connection, the northwest PATH, the south exit/Union Plaza PATH connections to the ACC/Southcore/Waterpark Place, the skywalk PATH, and the 4 teamways' direct north/south exits on Bay and York streets. In comparison, the people that would be affected by the market are those using the two main front doors, or the Via Arrivals Concourse door with the ramps up to the two main front doors, who wish to walk along the south side of Front St. People who use the teamways, or are just walking along Front, can use the north side of the street too. I think there's plenty of space for those remaining people with the market in place.