Rather nice game basically, professional-looking and with interesting changes from the run-of-the-mill tower defense games - combination of units and towers, some attackers shooting back at towers, directionality of units and airstrikes, etc.
However, it does have some serious deficiencies. I think the one that most bothered me was that reinforcement units (as opposed to towers) don't show their range of fire while being placed, so they are easily left out of useful range.
Also: the minigun turrets' range is often too short and doesn't cover the road, I think think this shouldn't be so when there's so little money; the shotgun turrets OTOH are not very effective. I completed the game with only few of the available upgrades - not enough upgrade points, and they're not even affected by my level of success in a mission. In-game tower upgrades are boring - same price always, just add another barrel. And the game lags quite seriously, apparently when there are many bodies on the screen.