I have 350K kms/220K miles on my particular unit.
Reliable? I think so. Almost stranded me once with a clogged EGR valve but removing the electric clip from it and I drove her home with only the CEL on.
The engine is VERY particular regarding service and oil/filter quality. You don't push the service window reqrdless of using synth oil or not.
In this time I've owned her only replaced 2 injectors, re-"O"ring'd them twice, on my 3rd EGR valve, 2nd FICM, couple alternators, 3rd set of battery's, serp belt tensioner, new rad and a few sensors. BTW I turn all my own wrenches on the truck, never been in the shop except for emissions testing - not that bad a truck to work on really and I don't consider the money I spent on parts or the things that have gone bad to be that far out of whack for a truck that's over 10 YO with this much mileage on her. She is a daily driver.
Transmission and attached drive train is as solid as anyone elses, maybe even better on occasion.
I'd buy another one in a heart beat.......but maybe it's just the devil I know that I trust more than the one I don't.
BTW ANY used diesel truck from ANY manufacture is going to cost LARGE for shop time if anything goes wrong and eventually it will. Eyes wide open when buying a used late model diesel truck from any of the Big Three. If you have an aversion to large shop bills or are paranoid about internet lore that you'll be stranded at the side of the road, buy a new truck with a warranty.