Brandon C. Schindwolf's Toki wa ima is a great paper on why Mitsuhide rebelled against Nobunaga. He provided his paper with all sides of the story. That being said, my favorite is on Luis Frois's opinion on Akechi Mitsuhide.
(Schindewolf, pp. 23-24)
"He explains that Akechi was a man who, through his own resourcefulness, foresight, and cunning, gained Nobunaga's favor, though not being of any noble orgin. However, to those in Nobunaga's inner circle, Akechi was an outsider, and was not held in high regard--but ever so, Akechi had a mysterious or strange way of holding on to, and even increasing his standing with Nobunaga. A man prone to betrayal and to secret gatherings, cruel in handing out punishment, and a despot who was shrewd in disguising himself, he was skilled in conspiracy, strong in perseverance, and a master of deception and scheming."
Tenka no tame!