Just a couple of weeks ago, the ICS update came to the European version of the Samsung Galaxy Tab 10.1 WiFi edition, and now it has begun rolling out to the U.S. version as well. You will now be on version 4.0.4 of Android, and Samsung version IMM76D.UELPL. If you check it manually and don't see it yet, you can always grab it with Kies.

Source: GalaxyTabForums.net