Great review, Jim. I just built mine and I totally agree with your verdict.
I saw another issue, that was not mentioned here I think (it was reported by sariel though), which is that the steering direction is oposite when the cabin is rotated (facing backwards). If the steering wheel itself would not rotate with the cabin, there would not be a problem, but I dont know yet how to implement that. There is little space.
In my opinion, adding a pneumatic compressor in the model would make it even better (all tractors are equipped with hydraulics).
I have same problems, and have read it multiple times, so prolly no mistake you made