Next is a GREAT read. This is two reports from The Sunday Times in London, they planned a 540 mile trip through Europe with 25-33% city driving and the rest expressway. Granted the expressway was 75MPH or so which I'm sure really hurt the Prius, but it's a great read how the Prius driver was struggling to go as slow and coast as much as he could, didn't use A/C or the radio. While the BMW is like, I blasted my A/C and could have gone much faster but I slowed down so he could keep up :-).
Speaking personally, the lighter 320d I drove in Germany got even better results, I got 40MPG at 100MPH for 3-5 hour trips and could easily get 50+MPG if I took a country road at 50MPH.