Nothing.
I love my Ranger. I was pleasantly surprised with the build quality of this little pick up truck. I still will not purchase a Ford car because of their notoriously famous POOR build quality, but would not hesitate to purchase any Ford Truck. No sqeeks or rattles, decent gas mileage for a 4.0 liter 6 cylinder, and a well designed interior. I know it is no 3 series BMW like my previous car, but more practical is hauling larger loads.
As far as the cars go get a 3.0 Ford. That is very hard to tear up.
My family has owned a number of Ford cars as well as 2 5-Series BMW's. The Ford cars were actually more reliable than the BMW's. One of our Fords went over 250,000 miles with only routine maintenance, and several made it well over 100,000 with no problems. Ford build quality (both cars and trucks) is definitely very good. A good example of this is the tremendous increase in reliability of both Jaguar and Mazda after Ford took them over.
As a mechanic I can't imagine where Ford cars became "notoriously famous" for poor build quality. Ford build quality is world-class for both cars and trucks, and as the previous comment states, the reliability and build quality of Jaguar and Mazda both went WAY UP after Ford took over their quality control. Jaguar has gone from being very unreliable to being one of the finest luxury cars on the road since Ford took it over.
If you really want an example of poor build quality, look at a Nissan with several miles on it!!
I absolutely LOVE my Ranger, my first Ford & simply the best, most reliable vehicle of any kind I've ever owned. MUCH better than my Honda Civic which self destructed in only 6 years of perfect maintenance & countless deceptions & fights with the Honda service staff. By the way, to maintain my Ford Ranger costs less than half that of my Honda Civic. Also, Ford has treated me many times better than Honda ever did. I will never buy another japanese car again, similar experience with Toyota. I love my Ranger and so does my son who just bought an '08 Sport. Excellent vehicle and strongly recommended to anyone sick of the expense & false hype surrounding Japanese vehicles. I have had absolutely No problems of any kind with the Ranger or my Ford dealer. Thanks Ford!!