I've only experienced one all digital AM so far, and that is (was) KTSN "Sun Radio" in Austin. It's just 1 kW from a stick right in the middle of the city so reception outside the urban core was pretty spotty. The audio quality didn't really seem any better or more immune from dropouts than the hybrid digital mode from what I remember. It was especially difficult under highway overpasses.
At night, reliable HD decoding was limited to maybe two blocks around the tower. And I know, because I drove all around it looking for the cutoff point! Like WYDE, it's a graveyard frequency so I expect nighttime digital to be equally useless on 1260.
That said, 1260 is at least 5kW during the day so that might help. Crawford's 850 is probably the best sounded AM HD I've heard anymore so maybe they can work some magic on 1260.
I understand that KTSN has now moved to 1060 and 1490 in Austin is doing a Jack FM feeding a translator. Still in full digital, as far as I know.