I've just finished building my first ArduCopter.  As I started testing I noticed that when I am increasing throttle, its not a smooth increase. At first there is a little "lag" and as I keep going up the throttle, when I get about half way up, the motors spike and gets really high. I am using the APM 1.0. I've gone through all of the steps to set it up including ESC calibration and radio calibration. Has anyone experienced this of have any insight on what the problem might be?