Also since March a professional model has been built for the sales center. This model includes guardrails and mullions, details missing in the previous study model. These images (taken by BVictor1) were found at SkyscraperPage Forum (full thread here), but the ominous sky is my addition.

The very bottom of the image above illustrates how the guardrails break from the contoured slab edge to separate terraces for different units. This functional design response also adds another layer to the contouring of the facade.

I'm gonna go out on a limb here and guess that this building will replace the First National Bank Building (now Chase Bank Building) as coolest building to look up at from below.
(Thanks to David G. for the head's up!)