Just a quick two cents: the
4E Manual of the Planes is actually my favorite book so far for
4E, and I consider it (if not indespensible) a fine tome. I would agree that it could have used more "crunch content" than it had, but the extensive details on the new cosmology, the background and setting data, and the general look and feel of the book were excellent.
Things I wish had been included: more monsters, some planar races for PCs (no Bariaur in a MotP book? Gah!), and perhaps a "ready to go" location in the Planes for time-tested DMs. That said, I hope they plan more follow ups to the MotP, because the new direction of planar adventures is a welcome change from the older cobbled-together cosmologies.
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"...an incredible panorama of interstellar battles unfolded before them. They saw fleets of heroes, armed and armored with the weird science of the future, locked in combat with strange enemies on a hundred worlds--the
Space Hag, with her terrible armies of the living dead, and the
Red Slavers of the Demon Stars who spread out their light-league wide gravity nets to ensnare the bright fleets, and the
Black Dragons of Nephog Quun with their uncanny power to control the future."
--Tower at the Edge of Time, Lin Carter
Zodiac Gods Publishing:
http://www.lulu.com/camazotz
Ancient Worlds Multicosm:
http://www.angelfire.com/rpg2/ancientworlds 
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