I installed the Haywood Variable Speed pump a couple of months ago. For me, the savings are dramatic.
My old pump ran about 2kWh for 8 hours per day (this is Arizona, and the temps are consistently above 100).
The new pump runs about 90 watts per hour for 9 hours and 2kWh for 3 hours daily.
The rate of kW is programable. The 3 hour cleaning cycle and the 9 hour recycle works great here.
I could reduce the cleaning cycle to 2 hours and the recycle to 7 hours, but the pool is sparking and well maintained now.
While the pump is running, the readout actually displays the electric usage in real time. There are many settings for timers and for pump speed. Our utility company provided a $200 rebate. The added bonus is the super quiet operation.
BTW - On 1/1/2012, Arizona changed its law that all new pool pumps must be either dual speed or variable speed.