Powell has always been a press untouchable, and nearly everyone in the mainstream media fawns over his loyalty to superiors even if it's at the expense of truth. And had Powell resigned in the run-up to war, I'd have bet money Cicero would have talked **** about him then.
From a metaperspective, the endorsement is important because it solidifies the view that the adults are in charge. It gives Obama another stamp of approval from the establishment, and on the military-side from this highly respected figure. What we're actually talking about here is political currency, which is valuable because people think it's valuable.
I waver on Powell. I very clearly remember overhearing people on Feb. 6th (Ronald Reagan's birfday) saying Powell sold them. This young white woman in an economics class said, "Well, I was unsure, but he changed my mind." I think it was U.S. News and World Report who quoted Powell saying "this is ********" when he was vetting evidence to put forth at the U.N. Liberal Powell lovers want to sell this story about the guy deceived and bullied; a well-meaning but unwilling enabler, and perhaps that's partially true. Powell's loyal aide Larry Wilkerson has been on a bunch of documentaries criticizing the administration, but mostly focusing on post-invasion incompetence.
You have to separate the man from the position. I know people who hate their job, hate having to be dishonest to customers, or be complete aholes and bitches, but it's basically a job requirement, they need to eat, and it's not something they want to do forever. Powell decided not to go on for a second term, but he was still lying. He might be a nice guy, but he also made the decision to undermine his own credibility.
Ben and Chris Rock are both right -- he could've been president. In retrospect I think we can say he's not up to the job (Donald Rumsfeld walked all over him).