[onewhippedpuppy]

David, I would say that your biggest concerns, aren't really a concern. For weight, compared to the overall weight of the truck, the additional weight of the AWD system is negligable. Gas mileage, normally the AWD versions of similar trucks take a 1 MPG hit or so. Again, not major. Understeer......it's a truck. It will handle like a pig regardless.

I had the opportunity to compare my Silverado and a Sierra Denali that my wife had as a loaner while her SRX was in the shop. The Denali had a LOT more power than my 5.3 Silverado, higher ride height (obviously), less accurate steering (2wd has rack and pinion), and a bit more body roll. Unlike my Silverado, I couldn't get the Denali to spin it's tires from a stop(I tried). The Denali was a very nice truck, the perks more than made up for the negatives.

The only concern I ever have with AWD vehicles is the additional stuff that can break. Otherwise, I think it's a bit of a wash. Around here with our snow and ice, I won't buy my wife a 2wd SUV. Personally I've never had trouble with a 2wd truck in the rain, but if it's a concern of yours you can't go too wrong with the Denali.