Let me preface this review by saying that I purchased the first 4400HST that arrived at my dealer -- it was a TOTAL POS -- millings had been left in the transmission housing, mixed with the hydro fluid and destroyed the brakes, transmission, hydraulics, etc.
Also, the JD engineers had the front end so screwed up that in 2WD it would leave 30 ft. arcs of dead grass when mowing the yard. I was never permitted to talk to the area JD representative about the piece of green junk that required over $12000 worth of warranty repairs at 50 hours.
Fearing more problems after it was repaired, and JD refused to take it back -- I liked its size, features and capabilities well enough to spend $5000 in trade a few months later for the exact same model that had been correctly engineered and it has been pretty rock solid for 10 years -- the two main hydraulic cylinders on the FEL needed rebuilding twice in two years but otherwise, VERY dependable.
It has been a real workhorse in mowing, blading and FEL 430 use for myself and neighbors. However, because of the $5000 extra it cost me to obtain one that was built right, that was the last JD product I will ever own.
When it came to buying a commercial ZTR mower, green was not even considered. I have had 2 Kubotas and 3 JD compact diesels and admit that the Kubotas were more dependable but had poor ergonomics.