Think of it as Dota-lite. The game's easy enough even my wife can play it. It doesn't have any of the twitch elements from DotA like last hits, juking, creep denies, lane control, etc. There's also less skill selection and item selection, giving it a much lower learning curve. They did add some things like purchasable upgrades to your army/exp/gold-per-sec/etc and those are kinda nice.
A lot of people who say they play dota a lot don't even know what those terms mean. If someone tells you they used to play a lot of Dota, first find out if they even know what those terms mean before you even listen to them. Otherwise, they're coming from a shallow dota background. I say this because a Lot of people say it's better than DoTA because Dota's imbalanced. DoTA's not imbalanced - that's a common misconeption new players get after getting completely owned by someone who's good at the game. It's never the players fault. Must be the imbalance... yeah, that attitude is a pet-peeve of mine.
Overall, here's my feeling of the game compared to dota.
Dota
+more competitive
+takes a lot more skill than Demigod to become good
+huge, huge hero selection. So many possible combinations make it have extremely high strategic value
+very very responsive controls.
+well balanced. Yes it's pretty well balanced. Usually it's the noobs who complain it's not.
-outdated graphics
Demigod:
+games are quicker
+less stressful to play than dota since most of the twitch stuff is removed
+easier to learn (takes maybe 30-60 minutes to learn every character and every item. Of course, it'll take a little longer to get the nuances, but at least you'll know what you're up against)
+nice graphics
+purchasable army upgrades and flags give it more high-level strategic options. Now you have to decide if you want to spend your money on items or buff your team. Capturing flags also present you with an opportunity cost of not being in the battle to gain exp (unless the flag is in a lane).
+I can't speak of the balance as I haven't played enough to notice any glaring flaws. It seems pretty well balanced, though.
-controls are sluggish. Heros don't immediately respond. Sometimes they don't respond at all (never happened to me, but my team mates complained about this before)
-pathfinding is really really bad. REALLY bad. To avoid getting stuck, you need to click a couple feet in front of him and spam those clicks.
-lack of a clickable minimap makes it a huge pain to quickly jump and look at another hero. You have to zoom way out, edge scroll over to them, then zoom way in.
-most of the hero's abilities are taken straight out of DoTA. There's very few new skills in Demigod that aren't already in DoTA.
For me, unless they beef it up with a lot more content soon, I'm not sure how much staying power this game has. It doesn't feel like it's got long legs. It's pretty fun though, and if you're looking for something new you may as well give it a try. I don't think it justifies the $40 price tag though since it feels like half of a game.