Nothing so far, in the 10,000 miles I have put on the truck.
Only upgrades I have installed are a pair of Vent-visors and a K&N air filter in the stock filter box.
I have never owned an American car before and I can honestly say I'm IMPRESSED! The seats are VERY comfortable and the 4 doors are very handy. Stock stereo system and speakers meet my standards for audio quality. OH YES and the shift on the fly 4x4 comes in handy on those snowy/icy days here in IL.
The two things I don't like about this truck:
Automatic transmission is a joke, its lost most of the time when it comes to shifts.
Finally, FUEL ECONOMY! Most cars I have owned get at least 75 miles to a 1/4 tank. On the Ranger I am lucky to look down at 3/4 a tank and see 45 miles on the tripometor. It leaves me thinking there is a hole in the gas tank. :-)
Could be hole in the tank or could be bad gas reader.