An initial rendering was leaked to the press last year. The designers stressed it was far from finalized, which is evident in the updated renderings. Here's a side-by-side comparison. You can see the base has changed, and the tower itself integrates much more glass than before, which gives it a much sleeker, modern look.
I also put together a very crude photoshopping of the original design last year, as viewed within the overall skyline. Compared with the renderings posted in today's statesman, the scale is not far off...though a bit shorter (and wider). This shot is taken from the I-35/Ben White Freeway flyover about 3-4 miles south of downtown
This scale on this one was a bit off (shorter, and wider), but the placement in the skyline is about right. This is taken from the Myers track stadium on the UT campus, north of downtown
