SGR

When you learn what happened to his kid, with the train crash, his drunkenness becomes a bit more understandable.

I agree. Civil service reforms, built up the navy, and given the circumstances of his ascendancy, I think he did a rather admirable job, especially when most figured he'd be a puppet of Conkling's machine (given his history), but instead, he followed a more honorable path and proved to be a foil to his old ally. Chinese exclusion act will probably forever be a stain on his legacy, but I think the historical consensus is that Arthur wasn't afraid of trying to go against the grain of what his old allies wanted because he had Bright's disease and knew he'd die very soon.