I think they've done a lot of good here, but think they could do certain things a little better.
First off - the stage is awful, especially the cover. It would be a shame for all their efforts to be held back by making an eyesore of one of the focal points.
It's not 'spectacular' but I like the media wall idea, especially how much of it will be a more mesh type for more simple effects and not video or advertising. It will add to the ambiance if executed properly.
I'm not impressed with the trellis running down the east side of Library Square. It needs to be there to both help frame the space and provide cover for vendors and such - but it would better 'complete' the square if they repeated the green covered portico here, and added the trellis to each side of it, as they seem to be doing by the coliseum. It will be a nice touch there, but the area would look more 'complete' of they did the same thing south of City Centre Dr as well.
There doesn't seem to be any permanent accommodation for vendors, which would help draw more people to the square. It's easy to stage events, but there has to be more than just an empty space to make people use it. Street meat, coffee/hot choc, roasted chestnuts, news stand... something. These could be permanently housed under the portico if they went with my idea above.
I'll take a closer look tomorrow. I just got back from Vegas and need to sleep ~