I just got back from a weekend trip in the mountains of PA on a 1200 GT Pro. Over the course of 514 miles we averaged 74 MPH (not including time stopped at gas stations) and, based on my Fuelly records, averaged 46.9 US MPG. The Tiger's in-computer MPG estimate was a slightly more optimistic (less accurate) 47.5 US MPG.
That's with panniers, but no top case and just a single rider. Front tire was aired to the recommended 32 PSI cold, and rear was aired down to 39 cold. Ending odometer was 1,972 miles (meaning I'm out of the break-in period, but not by much).