I've had my Avalanche for a year now. Great ride and comfort. Buttons for most things are fairly easy to find. Better ride than my old Tahoe was, and I put 175K on that one. 4WD works great in the mud and the sand. Tows like it doesn't have anything hooked on behind it. Great acceleration, and better brakes than my old Tahoe as well. Gas mileage is about what one could expect. I'm averaging about 17-18 MPG on the highway and less in town. Large fuel tank is a definite plus. Thinking of trading for a newer one, just to get a different color and some other options. Sound system is very nice.
Seat comfort, 4WD, and of course the ability to switch out the back end for more space.