I write this from the plane on the way to Redmond which is where Gas Powered Games is located.
Normally, publishers and developers have very explicit division of labor on projects. The developer makes the game, the publisher takes that game and markets, distributes is, and supports it.
As people observed with Sins of a Solar Empire, you can get tremendous results when the developer and publisher combine their teams together into a single "big" team.
That means Gas Powered Games will be intimately involved in the marketing of Demigod and it means Stardock will be very involved during development. At GPG, I'll be sitting in the "bull pen" with the development team working on the game itself. And together, we will be able to tap into the combined team's resources to get things done much more quickly.
Of course, the crucial element that can't be forgotten is the public beta program. Here's how it works:
We get the first beta out to you sometime in the first week of September. The goal here is to just see how well the thing works on people's computers. It won't be anywhere nearly fully functional. But we'll rapidly be enabling features and getting feedback which we'll be able to address.
AI needs help? AI developers at Stardock (including myself) can help. Need more map elements? Let us know and we'll see who is available to help on that too.
Similarly, advertisements and promotions for the game will get posted here before they go live typically. Art work, ideas and concepts won't be from Stardock's marketing team alone but rather the Gas Powered Games development team as well as anyone else.
One of the reasons why the Sins of a Solar Empire ads came out so well is because Ironclad (the developer) was so involved in the actual creation of the ads. It also didn't hurt that we put out the ads on the forums before they went to print where fans could make suggestions on how the ads could be improved.
Right now, we're playing the internal beta. The part that we're most challenged by at present is how quickly we can implement the Hamachi-like multiplayer system so that players who don't know what router ports are and such won't have to worry about them anymore. The first beta won't have that in there (I'm not sure as yet how much, if any, multiplayer will be in the initial beta 1 engine test portion).
One other thing players may find interesting is that GPG and Stardock have nearly a full year of free updates planned for Demigod. While the single player portion of the game is very important, our hope is to make Demigod the preeminent multiplayer strategy game for tournaments and such since the actual game-play is supports a lot more team mechanics than the traditional Starcraft or even Supreme Commander model would.
We'll have a pre-beta 1 showing at PAX in Seattle this weekend. If you're in the Washington area, be sure to stop by the Penny Arcade Expo. Chris Taylor and I will be giving live demos. 
-Brad Wardell = Frogboy = Draginol