Very enjoyable, but very difficult
To really enjoy it you have to play several times, and develop some strategy to survive... Also, without registering to GamerSafe your achievements are forgotten, and they're helpful!
It took me a bit to get used to the silliness of the game but it was cool :) The music was annoying though and I turned it down (pity there is no option to do this in mid-game!).
Enemies were indeed difficult to kill, and the chickens for example didn't cause enough damage to be useful considering the low rate-of-fire. Repairs are extremely expensive, compared to other games of this kind!
It might have been nice if weapons 8-10 (or even 7-10) could be fired immediately by pressing the number rather than just selected; I anyway found myself holding the mouse button constantly with weapon #6, and while at it pressing one of 7-10 and immediately 6 again - but then sometimes the other weapon didn't fire yet...
Well, got to wave 48 (with GamerSafe achievements), don't suppose I can do much better... Is there any end to this game? I did certainly enjoy it despite the few drawbacks :)