Recently purchased an 09 GMC 2500HD with the 6.6L Duramax diesel 4WD. Came from an 08 Toyota Tundra 5.7L and the GMC can not only haul twice the weight and tow 5000lbs more but it also rides smoother when empty. It returns 20mpg unloaded on the highway and the engine note is just enough to remind you that you're driving a diesel but quiet enough to be mistaken for a gasser. The interior is also a nicer place to be than in the Toyota, with more style and materials of a slightly higher quality. The Allison transmission is very smooth and always shifts at the right times. Test drove against the F250 and found the GMC a better all rounder, that stopped and accelerated better. Payload equal.
The drivetrain is second to none-huge power and refinement. Great payload of nearly 3000lbs, can tow 14,500lbs legally, rides and handles well for a truck. Interior features like bluetooth work well. Extended cab a better size than the F250. Looks sharp with optional 17s. Locking rear diff.
Their should be a sperate switch for the box light, very frustrating to have to turn inner lights on to get this. 13.8" brakes should be an option when the 17" rims are ordered rather than the same 12.8 discs that come with the 16" rims. Also, the stock shocks are junk. Needs Bilsteins.