I'm concerned about this subject too,
Supreme Commander runs fine in my pc, i hope Demigod does too
I'm running a nvidia 8600mgt 512, 2 gb ram..., vista home premium 32 bit, 2ghz dual core and the supreme commander demo runs fine, and the demigod beta ran even better (and if i ever upgrade my ram, even better than that).
This game is a real phenomenon, and when you get in a good match the tempo (and this opinion is based off the beta build) is perfect for how much i want to play games (30 minutes to an hour), and it's an exciting game. It's ranks up there with some of my all time favorites (battleield 2142, Sim City 4, Left 4 Dead and Hot Shot's Golf )