The update also adds enhancements to the notification screen which allows you to return calls, view pictures and video, and reply to email all directly from the notification itself. Voice Search will allow you to search the web using your voice, and speaks back to with answers to your questions. Also included with the update is the Smart Keyboard, which guesses the next word you are going to type before you type it. And with the update, voice typing can be done even while offline. The update also improves voice and data connectivity.
The Android 4.1 update for the Motorola DROID 4 will take 35-60 minutes and installing it will take another 15 to 20 minutes during which time no calls will be able to be made or received. Verizon does suggest that you have a full battery before attempting the download, which is software version 18.XT894.Verizon.en.US. The sad news is that this might be the last update for the phone, which started with Android 2.3 when launched.
source: Verizon (1), (2) via AndroidCentral