After hearing of this, I decided to try it out. Seems a compromise from many things I've heard. Simply accelerate at about 1/2 the Prius' capability. Then, set the cruise and try to glide whenever possible, not exceeding the speed limit by much.

I did this, attempting to drive at the optimal ~38MPH when possible on a trip to Borders and back. Took about 15 minutes each way with a 10 or so minute stop in between. Besides the intial warmup period, I must have averaged about 60MPG for each 5-minute interval! Considering my average tank mileage floats around 43, I'm thrilled. I better keep this up...

 

I too get up to speed rather quickly (probably pushing 3/4 down on the gas pedel). Then let up fully (feathering?) and set the cruise control at anywhere under 42 MPH (I heard you must keep under 42mph to invoke true stealth mode). 39mph works well for me. I seam to stay in "stealth" most often using this technique. Therefore increasing my MPG %.

 

As a quick update, I'm 80 miles into this tank and averaging 53! Admittedly, it's been 80 degrees out and I've driven unusually long periods of time. I'm sure it'll go down!