the hill assist works by applying the brakes when the car is on a hill (incline or decline). It comes on once the brake pedal is depressed and a gear is selected. It does not work if the brake pedal is released prior to selecting a gear.
Here is the annoying part. It's on a timer, not by sensing clutch engagement. I'm experienced enough to begin engaging the clutch even before the system releases the brakes. Therefore, I will be just sitting there w/ my clutch engaging and car not moving. This kind of wears out the clutch even if it's only a little bit.