Very good game. At first, I thought the best strategy was to use the guns and create a maze. That works pretty well, but I've since discovered other strategies that work just as well using the more advanced turrets as well. When the big towers get the range increase, they can shoot just about everywhere!
The only thing I can really ding this game for is that, as the maps get bigger, it becomes harder to see and yet the game gets faster, too. I got killed at Mistcastle because I couldn't see well enough.