I have put over 65,000 miles on my Avalanche in two and a half years. The only problem was that the tailgate latch broke. On the highway I get between 18 and 21 MPG even on the 75 MPH interstates. I have hauled 12 ft. 2x12's inside with the tailgate closed. The bed cover is secure yet easy to remove. In short it is a GREAT vehcle with multi-talents.
The lockable bed and the great gas milage for a vehicle of this size and power.