After the setback of iOS 4.2 that was plagued with Wifi issue, Apple has finally released the latest version 4.2.1 of iOS for all iPhone models except iPhone 2G, iPod touches and iPad. iOS 4.2.1 brings a lot of new features multitasking, AirPlay, AirPrint and improvements in many areas.
You can connect you iDevices, get the iTunes opened and force for new update check. Please note, if you want to to keep your jailbreak and unlock, don’t update your device to the latest version iOS except new jailbreak tools are available for download.
Direct download of iOS 4.2.1 for respective devices