Ken,
You already know more than the 4e MotP could provide. The 4e book isn't bad, but you know more about a planar campaign than joe average, and the 4e MotP is exceedingly specific in linking everything, fluff and game mechanics, to the default 4e cosmology (we're even seeing pre-existing campaign settings being altered to fit that model, first FR, next Eberron, and any future settings WotC releases).
The 4e cosmology has no yugoloths, no modrons, no guardinals, no eladrin celestials, no active Blood War (the Abyss and Hell are literally on opposite sides of the cosmos), no Outlands (nor anything covering the same metaphysical territory). The 4e default doesn't express the planes as being manifest expressions of any specific concept or alignment. The Astral sea is sort of a grab bag of astral domains that might as well be big demiplanes since there's no true organizing principle.
The 4e cosmology seems designed from the ground up for ease of casual use and tossing players and DM not used to running such games into the planes. It doesn't have the tone, atmosphere, and themes from 2e Planescape of clashing ideologies and philosophies (though to be fair that's not to say a good DM couldn't make it so). Perhaps summing up the difference between the two ideals of planar games espoused by 2e versus 4e - Belief does not equal power in the 4e cosmology.
You might find something to yoink in the 4e MotP, but knowing you and your background Ken, I don't think that you'll get much mileage out of it to be honest.