well, i did between 75 and 77 as best i could, with some traffic in the midst of all of it, and the re-fuel after about 20 miles of stop/go driving ended up like this:
Indicated on idrive:
Air temp 49F-53F
460 miles to empty, indicating the tank would last ~600miles - at one point in the trip, while doing 75mph after the fuel up, it was showing almost 660 miles to the tank (iirc, 560 miles remaining, 100 miles driven on the odometer)
Calculated fuel economy via fuelly was 37.1 for the 4 gallons i burned on the trip.
I can only complain a bit, but i really would love to get up toward 40 more often. In town, worst i've ever gotten was 29, which is usually the best that a 335i/s4 sees.