Originally Posted by KLOV
The game play was not supposed to be quite so difficult, but just before production started, the upper-management decided to make the game harder.

I think I remember something like this being mentioned in one of the interviews on Midway Arcade Treasures too... I don't remember the details or the reasoning though.
I prefer a game to be really difficult. That's what keeps it challenging. I'm not sure that the Williams games like Robotron or Defender would have acheived such legendary status if they were cakewalks. :-)