Thanks Ned for updating this. In regards to Steam I dont believe its the only option form what I have read. I dont know much about Steam myself so I could be wrong here.
Originally Posted by Ned
-AA3 coming to Steam
-upgrade to the Unreal Engine 3
-new training missions
-improved ballistics system
-evamped audio system - TeamSpeak3 Integration within the game.
-kill messages removed
-and more ...
Game Developers Conference 2009 - America's Army 3 Preview | ausgamers.com
The use of Steam is a surprise, at least to me.