Hey,
To be honest, I haven't mowed with it on the 850 yet this year. The lawn is JUST getting to the point of mowing here. Last year, it was aggravating on my old 715, but most of the problem I had was due to the too-slow speed, the lack of turning brakes, and the lack of instant reverse on the 715. These problems should be remedied with the 850.
Otherwise, my two biggest gripes were the solid mounting of the mower to the tractor and the fact that the mower stops every time you disengage the clutch to reverse, change gears, etc due to lack of live PTO. The sickle and rough-cut mowers have 15 degrees of tilt for going over uneven ground, but the finish mower does not. Due to that fact, it made me nervous about the stress at the mounting point between the tractor and the mower.
Funny you asked me about the mower tonight, I just had a long conversation with Joel about it on the phone today. He said I shouldn't be concerned about the lack of tilt. He mows an acre and a half all summer on an 850 and has never broken it over uneven ground. He did say that the price on them is gonna shoot way up to nearly 2 grand when his current supply is exhausted as BCS just took a significant jump due to a redesign of the gearbox.
Bill in WI