I've had an '81 model 1700 4WD for the past 10 years, as the second owner, which now has 1905 hours on it. Its been a real workhorse for me and has had very few problems. I had the starter and alternator rebuilt, and put new tires (mine has R1s) and battery on it, but that's it aside from routine maintenance.
The radiator on mine looks bad, as the prior (1st) owner let a bad battery leak on it and corrode it. It has held up so far but may get replaced this fall (New radiator is $325).
The only drawback to these tractors are parts are not generally available from after-market sources, so you are at the mercy of your New Holland dealer should you need anything major.
Good luck...