Currently our primary tractor is a John Deere 8530 with about 750 hours on it. We've had it for less than a year but it's been a good tractor for us.
Notice the two GPS antennas on the top of the cab. This is for the Leica MojoRTK system that we use for steering the tractor. The guidance system is accurate to within a few inches and it allows us to easily plant between the rows of the previous years corn stalks. In the next picture you can see a picture of the Leica reciever in the cab of the tractor.
One problem associated with planting corn between the previous years corn stalks is that the tires of the tractor are constantly running directly on top of the corn stalks. This tears the front tires of the tractor up rather quickly. To prevent this from happening we have installed a stalk roller on the front of the tractor.