The offers vary depending on the model.
For example, Astra offers 5 years of maintenance included but not the 2 year OnStar Direction and Connections package. For someone who's payment focused, think no-charge maintenace is a great idea. For consumers it's added piece of mind, and for GM it means not shelling out money for extra incentives today when they're looking to conserve as much as possible.
That, coupled with the longer warranty, are definite factors in choosing a Vibe over a Matrix if I were buying.