Like I said for just a sprayer I would not buy AWS. 

I would get it for a side dress rig if and when we trade.  I would down shift no doubt.  One question is why the AWS could not be limited by speed and not by a gear?  run second gear but any speed above 7 in that gear and it be two wheel.  It may shift down auto when you go that slow anyway, I can't remember. 

Not sure on your older rig, but the our STS you can down shift at full hydro.  shift button on the joystick so you would hit the master spray, down shift, and raise the coulters all from the joystick.  Now they have a new joystick I hear again for 2010.   We seemed to settle in on running the side dress at 9.5 to 10 mph so from what I heard we would be running in second gear and need to down shift on the ends.  The STS 10 and 12 may turn better but this 16 would greatly benefit from AWS when running the nitrogen bar.

We are running a field day next month along with Hagie.  Not sure what personnel will be up yet, but we will be going over a few items of concern I have.  More than one down there has my contact info if they want to discuss anything I have said.