I've been averaging 8.9L/100km (31 MPG Imperial, 26 MPG US) on my 5 so far, half commuting half highway. My trip to Seattle which was 90% highway mileage with A/C on most of the time was 8.1L/100km (35MPG, 29.5MPG). A week of commuting averaged me about 10.4L/100km (27MPG, too lazy to convert to US gallons) I'd like to see what I get with an upcoming summer road trip to Edmonton.
The best I did on my Corolla was 56 MPG Imperial. I'll miss the Corolla's fuel economy but oh well! I heard the 08 and 09 models use 1L/100km less fuel than the 06 and 07, I wonder how Mazda managed to do that.