SupCom and SupCom FA Retail now Registerable with Steamworks!
My Direct2Drive copies of both activate fine.
Forged Alliance keys have more luck with Registering properly.
But if you happen to get Supreme Commander gold from D2D. You get 2 cd keys (One for Supreme Commander and one for Forged Alliance Retail installs) which each activate a copy of Supreme Commander Gold collection on Steam.