Here's another video highlighting my experiences with the ShockWiz Tuning System for mountain bikes. This is a tougher trail, with more rock and twists and lips, and I'm convinced that I'll be faster, and smoother, because of this investment.
OH yeah—6 watts difference on my average power between the first and second lap, led to a 2.5 minute improvement over 4.8 miles. THAT IS HUGE!