I do wonder how well it will accommodate large crowds, but I think the closed in feeling for the plaza is probably intentional and will help it feel more intimate/festive. With the building to the west now being built, this is more noticeable.
In some ways I think this is better than Churchill Square (dare I say that) as a large, but not too large public space. I imagine in the summer it could be good for outdoor seating for nearby bars/restaurants.
It does have a lot of concrete, but it is designed to accommodate large crowds on a regular basis, so not much room for greenery. Overall I think it will do what it was intended to.