Just finished the game (on easy):
Every aspiring TD game maker should study this TD -- one of the best i've played. Best part was there was always some new tower or enemy to discover from start to end.
And I normally don't like TD games where you have to do manual clicking for some weapons, but this game had a great balance of that.
The only missing component was the ability to influence the path taken by enemies..
Overall a truly great TD game