Apple's iPad cut dramatically into Acer's sales this fall, IDC estimates showed today. In the US, Acer's computer numbers plunged 28.5 percent compared to a year ago, dropping it from 11.8 percent share at the end of 2009 to virtually tie Apple's share at 8.8 percent. Apple itself was the fastest mover and jumped from 7.2 percent a year ago to reach 8.7 percent.