Only had it a week, but here's my 2 cents....
Driving it back home after collecting it (300 miles) I had the cruise set to 60mph, and once at that speed I reset the average mpg and after 100 miles it was reading... you ready for this? I kid you not.... 30.8mpg!!! Seriously... I wish I'd taken the risk of getting my phone out to take a photo, as no one believes me now.
[edit]
Looks like mpg is seriously variable depending on how you drive it, and where, and at what speed.
[EDIT]
Just realised there would have been no risk in getting the camera out, as all I had to do was pull over... Doh! How dumb do I feel now? Was in such a rush to get it home, stopping was not part of the equation