Powell was just accepting his pre-employment bonus from the Obombme administration.
I think that's pretty close to it. Everyone knows Powell quit the Bush Administration out of disenchantment with his advice being rejected and the U.N. speech fiasco, which made Powell look bad and which (mostly) wasn't his fault.
He felt used and abused by Bush, Cheney, and Rumsfeld (so, I think, did George Tenet), so he took his marbles and went home to sulk with fellow ex-41 insiders like Brent Scowcroft.
I think history will vindicate Bush, find narrowly against Powell for going away mad, and find decisively against all the people who made Iraq worse than it had to be, by rendering aid and comfort to the nation's enemies for their own political purposes.
The point Rush made about Powell's promotion to great rank by Republicans -- without saying out loud that Powell was essentially a political general, like Clinton's puppydog Gen. Clark -- is a valid one. The Wall Street Wing of the GOP is the "ones what brung him", and he was vouchsafed further confidences and great offices by 43.
Powell does indeed appear to be angling for an Obama Administration appointment. Powell will have a long, quiet retirement if McCain manages to pull out a win.
Even if Obama wins, on second thought, Powell's phone may not ring. If Obama is smart -- and he is both smart and ruthless -- he will know instinctively that he doesn't have time for allegiance-switchers. It's one thing to bring a prominent Republican into his cabinet, and another to bring in one who traded his allegiances to bargain for the job.