Hey RobertSmalls, thanks for the Prius and CR-Z additions!
Agreed Frank Lee. This claim seems to be more common around folks who own fast cars, but I think it's more psychological than factual. I haven't seen much data that contradicts the "lowest RPM in highest gear" rule of thumb for peak mpg.
Found another one!
2005 Corvette 7.0L Manual
from Tested: speed vs. MPG, 2008 Corvette Z06 (505 hp)