Another thing that I've heard is that Toyota makes very 'tight' engines, meaning they are precise and exact in their fit, so friction losses are high at first until the components wear down a few nano-inches and loosen up a bit. It's a sign of high quality, but also does reduce their efficiency for a while when they are new, not to mention the computer is probably doing other things to 'ease' the break-in of the components and not maximizing the FE right away.
Bottom line is that if you had the non-hybrid version you would be getting a similar percentage less FE than with the hybrid version, and in the end that's what matters, regardless of the FE you are getting. EPA ratings are only useful for comparing vehicle to vehicle, they aren't very useful as a guide to tell you what you will get, especially if you live on a hill or something.
