Currently they've got the tutorial, the crab mission, the zombie mission, the dummy siege mission, and the dummy siege defense mission. At least in the demo.
And yes, the physics are excellent (with a few notable exceptions...), and I've never seen battlefields look so damned cool before, but that AI just gets me... I routinely have soldiers fling themselves off of cliffs as defense measures against approaching infantry.
This causes them to lose their expensive weapons, land helplessly at the feet of someone with a shotgun, and bump their head so they get an owie.
I've also never seen such incredibly stupid use of cover before. As soon as they see anyone, they will fling themselves to the ground, even if they're standing behind five feet of reinforced concrete.
Said concrete barrier will now obstruct their view, so they no longer see the approaching threat. They will wait a few moments, and then stand up since the coast is clear. The enemy is spotted as soon as their head reaches over the top, and they repeat the short-term memory loss duck-and-cover routine all over again.
But man, shooting the engine off a dropship and then watch as the forces slowly send it spiraling out of control, only to squash the troops it just dropped off into a creamy red paste... There's just nothing like it.
...except getting a rocket to do the same thing. Hot damn, that was awesome!
Also, I seem to have discovered what is arguably the most efficient defensive system available. I can easily go for half an hour or more at death-level spawn rates and not have a single soldier even get close to assaulting the brain.
Eventually though, the sheer amount of high-velocity rocket impacts will destroy the level, so defeat is inevitable... But still, for the rest of the time, I get to sit back and watch them make utter fools of themselves.