I purchased this truck used with 15,000 miles on it, I now have 45,000 on it 2 years later. I have had no problems with the truck mechanicaly. I tow a ski boat reguarly and fuel economy is only slightly effected. Only problems I have include, the leather seats cracking prematurly, and the dash has a few spots that are chipping. I get better than avertised with fuel economy, i get about 17 mpg city and 20 hwy with the 5.3L V-8. However, I do drive with a light foot and I have a bed cover on the truck. My father has a 2005 4wd Ford F-150 with an idetical bed cover and he gets better gas milage that that, however the chevy seems to handle towing better and is more manuverable.
Power, stereo, driving dynamics, look.
Better paint/rubber on dash, better leather (see what Ford uses it is higher quality).