I love my Avalance. I didn't think I'd like it at first, but it rides smoother than any other truck I know and having a weather-proof bed is great. I've pulled trailers and boats across country with no problem and it hasn't failed me yet. I think it is the most practical truck available, mostly because of the water-proof bed. The four wheel drive works great too, I've done some serious off- roading and haven't been stuck in a place I couldn't get out of with a little work.
As mentioned above, my favorite feature is the weather-proof bed and the ability to extend the bed into the back seat for extra long items. The smooth ride is incredible as well, better than any other four wheel drive pickup I've been in.
With any truck or SUV, the fuel economy could be better. I get a around 17 miles to the gallon on the highway and 15 in the city, but it's no worse than most trucks