Feed-forward gains have been somewhat of a paradox in the motion control industry. Typically, the use of velocity and acceleration feed-forward gains is helpful in improving tracking accuracy. Unfortunately, when these gains are turned up to their optimum levels, the axis gets extremely noisy because the quantization noise in the internal velocity and acceleration variables is pushed directly into the torque loop. (We sometimes refer to this as "torque chatter".) In addition to beating up the mechanics, this torque chatter causes the RMS usage to go up dramatically, reducing the usable continuous output of the motor.
The SST servo drives with the RAS enabled, create accurate, smooth internal representations of the velocity and acceleration so the feed-forward gains can be turned up to their optimum settings (without generating torque chatter). This increases tracking accuracy, and when tuned correctly, actually reduces the RMS torque usage because the motor is less likely to waste torque as it oscillates around the command profile. The scope shots below illustrate how effective the feed-forward gains become once the RAS is enabled. Notice the improved tracking accuracy and improved settling time:

Because RMS torque/force usage is typically reduced when using feed-forward gains, the motors will run cooler or can be reduced in size, enhancing your design options.