Is anybody installing?
For some reason the installer is downloading another 8 gigs. (Which makes sense since the pre-install was only ~7gb and the website says that a minimum of 15 gb is necessary).
by the way, if you downloaded the installer from battle.net, installed the initial 7 gbs, and then deleted the installer, then tried to run the Diablo III Setup.exe, it won't work (You will get unexpected decryption error). You'll have to redownloaded the 30mb...