We bought the E310 partly because we wanted the flexibility of the 1-10 dial for speed control.  We make kale and fruit smoothies every morning for breakfast.  Leaving the dial on 1, it is so easy to flip the "on" switch and then accelerate by turning the dial.  I use 8 large leaves of Lacinato kale, minus the stems, and the Vitamix reduces it to liquid in 10-15 seconds. It's a joy to use and to watch and the smoothies are a joy to eat.