NOTE: this was not the fitted one, this was a single flat one that you just lay down (the Bnip maybe?). Perhaps the fitted SKYDDA HÖGTworks better. If you experiment, post a comment here about the results!
UPDATE Oct 2010: The waterproof crib pads from BabiesRUS have proven to be much more effective; I have had them for about 6 months. They DO leech through to the mattress if heavily soiled but MUCH more absorbent overall.