Well, just for a quick update, the dealer came out, updated all three components and upgraded the system to the trial version of Terrastar C and turned off a bunch of unnecessary feeds in the data stream.  Running the "C" correction, the accuracy was great.  In 20" rows, I would bump the line 2" left or right on every third or fourth pass.  This is in knee to waist high corn so there is only about +/- 4" to play with before you start hitting crop.  Its pretty neat how the differential page will show you the real time  predicted horizontal accuracy.  For most of yesterday, it was running around 1" after a suitable convergence time.   The steady steer system is great and far surpasses any electric steering that I've been around to date.  The ability to reverse accurately is a huge step up.  The next step will be to see if they will honor their internet advertisement to provide a free year of Terrastar L with purchase of the 7500 receiver then to test out the accuracy of the "L".