Just to add a little more color to this (because I know what an alarming trend these Quant percentiles can look like): When we've talked to folks from GMAC, they're instructing schools to look at the scaled score for what it is, which is a fixed measure of ability. A 44 today reflects the same quant ability as 5 years ago, and schools know how that ability level performs in the MBA classroom. What's changed - largely because of the addition to the examinee pool of high-ability quant test-takers from emerging markets like the BRIC nations and slightly fewer examinees with lower quant abilities (who may not see as much value in a lower-tiered MBA or may try to "sneak around" the GMAT with the GRE) - is that a substantially higher percentage of GMAT candidates have that ability.
So don't let the 58th percentile scream "average!" at you - it's a little closer to the average of the current pool of examinees than it used to be, but schools know what a 44 means in terms of estimated ability.