Motorola has finally released Android 2.3.4 update for Atrix 4G customers on AT&T. This update available both via OTA and manual download.
Apart from the Gingerbread goodness, update brings several other fixes – like improvements in gallery, Music app, updated Motoblur, full 1080p video playback, the ability to dismiss one notification from notification tray, and faster webtop browsing.
This update also brings the app sideloading for the Atrix 4G users, which was earlier blocked by AT&T.
You can download the update from here or go to Menu->Settings->About phone->System Updates to check for OTA.
Full Update Release Notes here