I have had the complete Power Pack on two V10's including the 2010 that I am driving now. It significantly increases low end torque. The result is much better climbing ability in the mountains and better acceleration. It helps gas mileage slightly. We drive in the mountains a lot towing a CR-V. IMHO it is well worth the expense. The Power Pack includes headers, exhaust and the ability to tune the computer chip.
The other thing is that I have been a gear head since I was a kid, and I love the sound of the engine. Vroom vroom!