I am aware that Lincoln tried to hire him, but I don't think that tells you much other than that Lincoln was keen to have a good general on his team (and no-one is disputing Lee's military prowess).

He certainly seems to have been less egregiously awful than Davies or the repellent Stephens, but there is good evidence that the idea that he was a particularly considerate slave-owner is a myth (though it does seem to have been true of Jackson, who does seem to have been sincerely concerned about the welfare of his slaves and of the free blacks in Lexington, even if his views on the permissibility of slavery are regrettable, and this might play into the attitudes of some of his descendants).