Danny overcoming his inner demons and genetically-linked alcoholism to achieve 15 years of sobriety.
Every scene of Danny ministering to terminally ill patients in their last moments. Special mention goes to the last one: Dan's foul-tempered, nearly compassionless coworker Fred Carling, who Dan spends most of the book hating until Fred is mortally injured by a drunk driver at the end of the story. Dan helps him die peacefully regardless of their feelings for one another, and implies that he means to give Fred's beloved dog Brownie a new home - with Abra.
Abra is so happy to finally meet another person like her that she practically jumps out of her skin. It's hard not to smile when she and Dan first meet up, especially considering how happy and relieved they both feel at that moment.
One of the last ghosts Danny sees at the Overlook is his father, who grins and waves to him before everyone leaves.
Not only does he show up and wave goodbye to Danny, it's heavily implied that he helped push Rose to her death, thus saving the lives of his son and granddaughter. Not a bad way to make up for what happened last time around.