I think I have seen 40 mpg once and that was with a virtually empty tank on a 40 minute journey but I don't have cruise.
I averaged 34 (Computer) on a 112 mile journey yesterday which I'm content with.
When I first bought the car I was bothered but not now. I typically sit around 28-32 mpg and its rarely below 25 mpg.
Just enjoy the car and been glad you went for the GTI and not the TDI
Its already been said its very dependent on your mileage and type of roads you drive on, if your motorway crunching then you wont see the best of the GTI.
I don't think I could stick to 60 on a motorway, I just get bored.