Picked up the 21015 set at the local LEGO store today. Not done with it yet, but it's very interesting. 5-sided, and even though I visited the real one in 1998, I don't remember the rocket ship inside it...
...and done.
I won't do a build report, but one neat thing about the build (besides the 5-sided structure) is that you don't make the base until the end. Keeps the mystery alive for a bit, but in the end how it's done wasn't exactly groundbreaking technique. Neat kit, and more sturdy than I thought it would be from the pictures. The core of the tower, inside the 5-sided ring, is built very much like the booster rockets from the big Space Shuttle kit. The only real downside was that the build did get a bit repetitive in the middle, which isn't unusual for the Landmarks series of Architecture kits, but this certainly isn't as repetitive as the Burj al Khalifa kit was!