As most probably know already, you can download the D3 client.
So far I've just seen the Italian client:
http://eu.media.battle.net.edgesuite.net/downloads/d3-installers/589acdb4-c660-318a-b993-01528fad7da6/Diablo-III-8370-itIT-Installer-downloader.exe (http://eu.media.battle.net.edgesuite.net/downloads/d3-installers/589acdb4-c660-318a-b993-01528fad7da6/Diablo-III-8370-itIT-Installer-downloader.exe)
I've heard from one person that some have used the sc2 authkey ( http://us.battle.net/static/mediakey/sc2-authenticationcode-enUS.txt (http://us.battle.net/static/mediakey/sc2-authenticationcode-enUS.txt)) to install the D3 client, although the D3 authkey (http://us.battle.net/static/mediakey/d3-authenticationcode-enUS.txt (http://us.battle.net/static/mediakey/d3-authenticationcode-enUS.txt)) is still empty. So I'm not 100% sure on how that is working.
If anyone has any other info or links to different clients or any other insight, feel free to post.
8)
Here are the other links enjoy.
DIABLO III Retail (enUS – America)
http://eu.media.battle.net.edgesuite.net/downloads/d3-installers/589acdb4-c660-318a-b993-01528fad7da6/Diablo-III-8370-enUS-Installer-downloader.exe (http://eu.media.battle.net.edgesuite.net/downloads/d3-installers/589acdb4-c660-318a-b993-01528fad7da6/Diablo-III-8370-enUS-Installer-downloader.exe)
DIABLO III Retail (EU – English)
http://eu.media.battle.net.edgesuite.net/downloads/d3-installers/589acdb4-c660-318a-b993-01528fad7da6/Diablo-III-8370-enGB-Installer-downloader.exe (http://eu.media.battle.net.edgesuite.net/downloads/d3-installers/589acdb4-c660-318a-b993-01528fad7da6/Diablo-III-8370-enGB-Installer-downloader.exe)
DIABLO III Retail (EU – Italian)
http://eu.media.battle.net.edgesuite.net/downloads/d3-installers/589acdb4-c660-318a-b993-01528fad7da6/Diablo-III-8370-itIT-Installer-downloader.exe (http://eu.media.battle.net.edgesuite.net/downloads/d3-installers/589acdb4-c660-318a-b993-01528fad7da6/Diablo-III-8370-itIT-Installer-downloader.exe)
DIABLO III Retail (EU – French)
http://eu.media.battle.net.edgesuite.net/downloads/d3-installers/589acdb4-c660-318a-b993-01528fad7da6/Diablo-III-8370-frFR-Installer-downloader.exe (http://eu.media.battle.net.edgesuite.net/downloads/d3-installers/589acdb4-c660-318a-b993-01528fad7da6/Diablo-III-8370-frFR-Installer-downloader.exe)
DIABLO III Retail (EU – Germany)
http://eu.media.battle.net.edgesuite.net/downloads/d3-installers/589acdb4-c660-318a-b993-01528fad7da6/Diablo-III-8370-deDE-Installer-downloader.exe (http://eu.media.battle.net.edgesuite.net/downloads/d3-installers/589acdb4-c660-318a-b993-01528fad7da6/Diablo-III-8370-deDE-Installer-downloader.exe)
DIABLO III Retail (EU – Spain)
http://eu.media.battle.net.edgesuite.net/downloads/d3-installers/589acdb4-c660-318a-b993-01528fad7da6/Diablo-III-8370-esES-Installer-downloader.exe (http://eu.media.battle.net.edgesuite.net/downloads/d3-installers/589acdb4-c660-318a-b993-01528fad7da6/Diablo-III-8370-esES-Installer-downloader.exe)
Currently it's impossible to install it, video below shows how far can you go with SC2 authkey.
Diablo III - Release Installer - Datamine Progress 1 (http://www.youtube.com/watch?v=ulKXi6qlQvQ#ws)
It fails cause authkey isn't right and it can't get right files and read them. :'(