According to Samsung, apps, widgets and wallpaper are reset to default settings although the Lock Screen image will remain. You can keep the SIM card and microSD card installed while updating. The app menu will be reset, but all downloaded apps will be kept which we're sure brings you some relief. All contact and contact groups will remain although contacts within the contact groups will be removed. Email accounts added from the Social Hub or a premium Samsung account will be removed. Music playlists and settings (Equalizer, Sound effect, Music menu) will be reset and paired bluetooth devices will be removed during the update.
Besides installing Ice Cream Sandwich on the tablet, the update adds stability improvements to the AT&T Samsung GALAXY Tab 8.9 LTE. Once you've updated your tablet you can tell us what you think of the new OS build by dropping us a comment in the box below.
source: Samsung, AndroidPolice via AndroidCentral