First off, I just wanted to say that I'm a big fan of Stardock. Your mindset on the games you release remind me in a way of Blizzard Entertainment's old mindset on games. (The Preworld of Warcraft years) Your previous releases have amused and entertained me in a way many newer games haven't. (Specificly, Gal. Civs. 2, Sins, and now Demigod.)
Either way, I just wanted to say that I've found Demigod to be extremely enjoyable. The gameplay, though simple, manages to feel different from many other newer RST games. Most newer RST games boil down to little more than a game of Paper-Rock-Scissors, with a few added features here and there. In the past few years, I haven't found many RST games to be very innovative. Sure, you might find an RTS here and there with new bells and wistles, but after sitting down and playing with them once or twice, they end up being just another RTS.
What I like about Demigod, is that it doesn't feel like your trying to be overly innovative. I like the simple and smooth gameplay with lots of variety, but very little of that "Paper-Rock-Scissors" feel. Instead, this game feels like it might be right at home in a late 80's, early 90's arcade setting, right next to the "Gaunlet" machine. Meaning, that desides the graphics (Which are obviously superior to "Gauntlet") this game's general playstyle was designed with more of an Arcade's "Simple, Fun, and Addictive" mindset. Games are kept short and sweet, and once your done, you just want to pop in more quaters.
Unlike more RTS games these days, this game doesn't feel like an overly complicated "Paper-Rock-Scissors" and feels more like a Tug-o-War. Which, although not exactly innovative, is a nice break from the minotony of yet another generic RTS. The only time that Demigod really feels like other other RTS games is when you've out resourced the opposition, it's all downhill from there.
Maybe you could add some sort of mechanic that can help turn the tide for the losing side? Some sort of super-attack that you can only do after x-number of deaths? Some sort of super-solider that you can summon out of the portal when you feel like the battlefield needs some equalizing. Just a little something for the underdog, if only so the outcome of the game isn't nessissaraly written the moment one team takes the lead.
Bottom Line is, this game is fun in a simplistic way, and I love it!
Overall, I give this games an "B+" But I can see it becoming an "A" once some of that add-on content becomes available. (Hopefully you won't charge too much...)