Won't work through the downloaded .exe file or through running gu.exe. Either way, I get the message that HOMM6 is "not yet installed."
Two other odd details. First, when I run gu.exe, the message that comes up as it's trying to install relates to the "closed public beta." Second, I think the patch downloaded through Steam on the first day it was released. Nonetheless, the game won't update.
I guess you have both beta client and heroes 6 game installed. Maybe you should try to uninstall beta client and main game ad delete folders created by game (install folder, profiles ect)
after that please try to install game - it should work fine