Alright, here goes...Gameplay wise first, art-wise later.
As a concept, Demigod is very strong, and it's influences are easily recognizeable, but with enough new mechanics and strategies to make it worthwhile. The balance isn't perfect, but stardock has a reputation for post-release support for their products, so that's not so big a deal. The visuals (in the strictly technical sense) are very strong without system requirements being too high for people who don't want to shell out a lot of money for a video card. Pantheon mode is a great concept, but until the matchmaking and networking is improved(and the bot players removed) it's hard to tell how well executed it will be in the end. But it SEEMS really cool, especially if there is some ingame reward other than favor items for having your demigod or side(light/dark) win. It'd be neat if every complete "round" of pantheon could reward winning players with some new content element for participating, and it would attract players to the mode. The more the merrier 
Art-wise, it's awesome. the maps and demigods are breathtaking to behold, both close-up and far away, and more importantly, they feel right for the game. A lot of other games lack the internal consistancy that makes a game feel like it has a coherant art direction. while there are some exceptions (regulus seems too human to me; he doesn't really seem like a demigod if he needs a fancy crossbow and gadgets), Demigod generally achieves that. The music is incredible too, and it tends to create tension at just the right moments.
As a game, demigod is simply awesome, but it's multiplayer nature means that the quality of the experience is dependent on the number and quality of the players in it's community. If a lot of people play and spamming and such is kept to a minimum, I can see Demigod as a game of the year easily. At the very least it should have a strong cult following for a very long time, and I intend to be a part of it 
All in all, a good review I think.