Today Apple released both iOS 4.3.2 and iOS 4.2.7. The first was for almost all iOS devices except the Verizon iPhone. The second was for the Verizon iPhone. Like iPad last year, which shipped with iOS 3.2 and didn't unify with the rest of the iOS family until iOS 4.2, the Verizon iPhone shipped with iOS 4.2.5/4.2.6 and won't unify with the rest of the iOS family until some future update, perhaps not until iOS 5/5.x.
Yet despite this fragmentation -- or more properly bifurcation -- of the iOS software, Apple still delivered both updates at the same time, across the world, and across both major US carriers, AT&T and Verizon.