Mark,

I don't have autosteer on a combine at this point, but I do on a tractor.  I would state that having a system that will remain engaged in reverse is a big deal.  There are many times that you need to back up and you want the system to remain engaged.  If for no other reason, just so you don't have to reengage it when you go forward again.  With a tractor, there are many situations where you need to reverse on the headlands for a short distance.  Having the auto steer keeping the tractor on line in reverse is a very helpful in those situations.   I would be very hesitant to buy a system that will not engage in reverse.