Good!
It's pretty decent. I've played it more than most of the games I've found here... still it could have more levels and it lacks a pause button.
On the last level, survival, after the 10th minute the stage is friggin' packed and there's no use having a lot of towers because the enemies won't die! (BTW, my highest score on survival is 16:53)
To the developer:
-The awards are a great extra, I would keep on playing it just to get 'em all.
-Unlocking an extra "master" stage after getting all the rewards would be awesome!
-Also a "create your stage" feature would be quite fun!