update to iOS to rectify what it perceived as a set of bugs in the system -- namely, an excessively large cache of location information that was backed up to iTunes and hung around even after you switched Location Services off -- is now being distributed to iPhones, iPads and iPod touches out in the wild. To exterminate those problematic aspects of your OS, you know what to do -- hook up to iTunes and get downloading. And yes, it's the full 666.2MB file as usual.
P.S. - iOS 4.2.8 looks to be out for Verizon iPhones as well, though we haven't verified this for ourselves yet. Still, it's the same set of changes and the same method to obtain the latest firmware.