A few bugs
Forget the "Its not original" howls, the biggest bug I ran into is with the ranged units, on a few levels towards the end they got collective downs syndrome. I guess they thought the best way to fight off a cannon is not with the bow and arrow that's killed everything else up to now but to run at it face first to give the operators a hand job.
That's my biggest issue ranged dudes deciding at random to melee.