mpoulsom just bought the single tall skinny version last weekend and it feels pretty darn sturdy to me....product bureau is right on for the suggestions.

decorox i've owned 2 expedits (both were 5x5, as pictured above) and moved it 4 times.The shelves are very sturdy -- I've filled more than half of the shelves with books. No sagging. It literally weighs about 200 lbs, so it's sheer size makes it difficult to move up and down stairs. when moving, we broke it down carefully (this project alone takes a LOT of space, dont lose the dowel parts) and took time to rebuild it. once it's up, it's a great piece -- one of IKEA's best contributions to design.