We sold exactly one of these ( http://www.unisteer.com/utility_vehicle_parts/john_deere_utv_steering_parts/xuv-hpx/4x4_hpx_xuv_series_gator_-_electra-steer_all_years.html?keyword=gator ) at my last dealership. It was to an older couple that had been driving quads together for years, but they were to the point that the quads just hurt them too much. They purchased an XUV Gator from me and by all accounts were very happy with it. Around 6 months after purchase the lady had surgery of some sort on her wrist and after that she could not steer the Gator very well, so they came in to see me. We set them up with the Unisteer system and they were very pleased with the outcome. Several of us test drove the unit before they picked it up - most of us liked the steering at low speeds, but none of us cared for it at higher speeds as it was too "twitchy" - and none of us cared for the 1K price tag. As it is not a speed sensitive system, it is not for everyone. How do you and your wife use your 850D? Also, I must mention that Deere has all but guaranteed us an optional Speed Sensitive Electric Power Steering System for the new 625i, 825i and 855D Gator XUV models this spring. So... In addition to your new tractor, you may find yourself needing a new Gator soon as well!
My wife uses the gator around our property to pick items in the garden. Some of the items are close to the house and others are back 1500 feet into the property. My wife is 5' and 100 pounds and sometimes the steering can be hard in the tight areas. 90 percent of the time the gator is at 20mph or less.
I talked with her about getting a new style with the power steering and I did not get a good look. I cannot imagine what one like ours would cost. We need the plastic roof, the metal bed guard so stuff does not come forward from the bed, hydro dump, brush guard & offroad lights. Plus I am spoiled by the diesel when I am spraying with it.
I bet thats 16K in a new machine... Not going to happen.