If this is Amazon trying to compete with Google's pricing scheme, they missed. Google's sustained use discounts just happen, and give you a discount on whatever time you used. With Amazon's new pricing for reserved instances, any reserved instance you buy (upfront fee or not) commits you to pay an hourly fee regardless of whether the instance is running now.

They removed the light/medium reserved instance options where you paid a discounted usage rate, and now just have 3 ways of purchasing a heavy reserved instance.

This is going to raise prices for us on AWS because we won't be able to use reservations for the instances we autoscale so the current medium reservations we have are going to be on-demand now.