I snuck a peak inside during construction. it is indeed amazing built. there is slight value engineering here and there, but nothing to take away. I hope to take a better (read: legal) visit soon and post it in my blog.
I have been following this project for years now and I have to agree, the built product certainly lives up to the ambitious design and to Coop Himmelb(l)au's design intent..its stunning in person! some clever devices at play in the roof really capture a futuristic and floating look