SeaPrius: Might be another case of "NSD". Any oldtimers remember this from the old Yahoo Prius group?
"NSD" is short for "Natalie Style Driving". Several years ago, when the Prius was new to everyone, there was a nice woman named Natalie who only drove her Prius on short trips of a few miles each, with about at least an hour between trips.
Since early model US Prius don't have the "thermos bottle" feature which now keeps new Prius' radiator fluid warm, Natalie got really low mileage for a Prius (much lower than what SeaPrius reports.)
I suspect SeaPrius may be seeing the result of a similar driving style, combined with the current relatively cool weather in her part of the US.
It's likely you'll see your mileage improve somewhat as the weather warms up, but if (if) you typically drive like Natalie, averaging around 45 - 50 MPG in your shiny new Prius is probably about what you should expect.
And, as others have probably suggested, you might try keeping around 40 (or 42) psi in all 4 tires to see if that helps your mileage.
In any event, you're still getting about twice the mileage of most of the other vehicles on the road!
Enjoy your new Prius!
- Peter
CA "MO MPG"
2002 White Prius