I ordered a 2011 GMC 2500 diesel pickup in December and it came in a couple of weeks ago. The sales guy said nothing about the DEF injection system back when I ordered it, if he had I would not have ordered it. Looking at a number of forums on the web about this system it is not ready for prime time. Owners, especially in colder climates, have been having a lot of trouble with this system. When the sensors in the DEF tank "think" that the tank is empty the truck goes into limp mode which essentially limits it to 4 mph. Needless to say owners are experiencing the limp mode when the tank still has fluid in it. Add to that the fluid has a 12 degree freezing temp and this has apparently been causing sensor malfunction. The system is controlled by the ECU which is also having software issues. I refused to take delivery of the truck and am going to order a gas truck until GMC sorts this out. I have also heard that GMC's placement of the DEF tank makes it susceptible to getting hit by road debris. Anyway would be interested if anyone who actually has one of these new trucks has had any issues with it. Thanks......JR