On all screenshots shown there's no real shadow, just a black spot under every unit.
Will there be a real shadow in the final game,
and will it move with the sun?
Long shadows at sunset.
And in the night, will the different lightsources cast shadows?
Of course you'll need a good computer if you want to have this kind of shadows AND many units,
but in the soloplayer-modus there won't be so much units and it would be no problem to turn them off.