Pros:

Great environment!
Well placed hordes, tanks, specials
non linear
nice attention to detail

Cons:

3rd and final map has invisible wall.  Tried restarting, nothing helped.  The wall is located at the very top of the hilll where the rock outcropping is.  Does not allow passage to get to final building.

Conclusion:

Overall, this is a great campaign.  Fix the final chapter and you have yourself a winner!