I purchased my 08 in October and now have 5000 miles on it. The fuel economy is around 16 in city and 18 on highway, but I am still in break-in period and expect improvement. Economy drops quickly north of 70 MPH. The Duramax and Allison are a great powerteam and while you can hear it shift, you cannot feel it. Interior on the SLT very well laid our and looks like it should be in a luxury car. The GM 100k warranty is a big plus. My only concern is the 26 gallon fuel tank is too small for hauling heavy trailers.