I just sold my '05 HAH/with Nav mainly because as an earlier adopter, I was expecting somewhere between 29 and 37 mpg, but only averaged less than 27 - this particular winter seemed worse - I was averaging 23.
All my friends were more than shocked that I bought a '07 Touring Prius with Package 6 which was the Prius version that most closely resembled the features that were on my Accord. I am tall - 5'9" (34" inseam) and the driver's seat is really my only beef. I too tilted my Accord seat so that the front of the seat was at the highest point. I will not be taking a long trip until Easter, but the seat difference is undeniable.
In the 141 miles I have driven my Prius, I am getting 36 mpg. I do love the back up camera and the bluetooth for my phone. It's warmed up, so I don't know if I will miss the heated seats - this winter was the first time I had ever used them.
I don't know what Toyota has planned for 2008. There are rumors of a total redesign, so maybe you should wait to see if they improve the seats.