I really like this game and have played it many times. But despite my enjoyment, I have many critiques:
* As someone mentioned the reset button is really close to the ammo recharge button.
* Having to constantly click the ammo button makes it tough to get other things done. I know it was an intentional part of the game, but it got tiresome really quickly and I worry about wearing out my mouse button over time.
* The towers that automatically make ammo take so much gold to buy that by the time I can afford to use them the game is almost over. And they don't make much ammo compared to my clicks anyway. I might feel differently if the ammo making tower synergized with the ammo click multiplying tower, but they don't.
* The money tower is not very useful for a similar reason: By the time I can afford it, the tower isn't that necessary.
* Buying multiple levels in a given tower doesn't seem much use. Cheaper to just buy more of the same tower.
* Except for the shooter towers, the bomb towers and the click multiplier towers, I really didn't find a need for most of the other towers in the game. Which is a shame, because they seemed like decently designed ideas.
* By the time I've gotten to level 8 or 10, I feel like I'm pretty much all set. There just don't seem that many challenges beyond that (those tower-dismantling guys are a little pain, but eventually handled). So at level 15 when the game ends, it's kind of anti-climactic. Maybe a couple harder modes or extra levels would be fun?
* Could use a few additional maps.
Having said all that, I'd like to reiterate that I really did enjoy the game. Neat graphics, generally decent play.