I would completely agree with everything said here - I went today and the centre is extremely underadvertised (you only really find it if you know where it is) and empty. There were a few people there (by that I mean the most I could see at one time was 10) and I sense the BBC article has maybe brought a couple more people who know the place is there, but I personally cannot visualise it being a major shopping destination.
Interestingly though - Brewdog seemed quite full? On the other hand, I walked past WHSmith and it was completely empty, exactly the same with Costa. As I have already said, personally I cannot see this centre being a shopping hub as realistically no business will be willing to move into a completely empty shopping centre unless they believed people would come just for that shop!
Also, the main shops currently in the centre already exist in the concourse, that being Pret, WHSmith and Costa (although currently closed). Passengers will most likely opt for the concourse level shop as it is easier to get to, or not know the shop in the sidings exists.