I have both the Electrolux Magic Mill and the Kitchenaid. Love all the attachments for the KA and use them a lot. Actually wore out the gear on the KA this fall, and DH bought the kit and replaced it easily.
It's a fiber gear and is the "weakest link" and does wear over time. But I'd rather have that then wear out the motor. So if you have one and it seems like it's slipping or stops mixing and the motor is fine, it's a real easy fix and your machine will be up and running.