after which I drove to work and averaged 42.0 mpg on a 33 mile trip that usually averages 38-40.

I know it's only a limited sample but it does appear that the update has a noticeable effect.

In addition, I picked up a 2007 Accord brochure. The hybrid is still shown with unchanged specs from the '06 except that fuel economy is now listed as 28/35 for the '07 vs 25/34 for the '06.

My guess is that the PCM update has brought my 06 HAH up to the same fuel economy as the 07. However, this is still lower than the listed fuel economy for the 05, which I believe was 30/37. My understanding was that most of the reduction from the 05 to the 06 was due to a change in testing procedure rather than a real reduction in gas mileage.

It's interesting and good news (in addition to your mpg) that there IS a 2007 Accord hybrid in the brochure. Earlier rumors were that Honda was dropping the Accord hybrid due to slow sales.