It was sad to see such a great character go, but it was a fitting demise if you really think about it. The foundation of Gus' empire was his calculating and logical nature. Even when he did something so risky as to wipe out the entirety of Don Eladio's crew, there was a methodical plan in motion and he stuck to the plan. In an industry filled with loose cannons, Gus rose to the top because he knew how to cover his tracks and stay in the shadows.
The decision that ultimately ended his life was one of emotion, not logic. Gus should have sent one of his lackeys to kill Hector Salamanca, but he simply couldn't resist the temptation of seeing the life drain out of the old man's eyes. His thirst for revenge against the Cartel was his one emotional indulgence. Once Walt caught wind from Saul of this weakness...well, that was the end of Gus Fring.
Some people are saying the whole Harvey Dent thing was over the top...I think it was absolutely brilliant. My jaw was just hanging open.