I've got almost 16K miles on my '07 SE V6 AWD with no issues whatsoever. I bought it early last March (I live in Massachusetts) and took it through one snowstorm. I was very impressed with the AWD performance! This winter the car has proved stellar. The AWD is not just for snow but rain, sand and other loose surfaces.
Make sure that the tech that you spoke with wasn't confusing the Fusion (with a Ford USA AWD system) with the Haldex AWD system used in the larger Fords. I work in the parts department of a large Volvo dealership where Haldex failures are quite common.
Using the on-board system, my fuel mileage is a steady 22mpg. A bit down from the 24mpg that I got on my '00 Chevy Impala but I fully realize the usefulness and safety inherent in the AWD choice that I made.
John