Although Acer laid out their Iconia Tab ICS update list not all that long ago, it seems there has been some issues in the Acer camp with folks actually being able to you know, update their devices. The updates, more specifically for the Iconia Tab A100 have appeared for the most part on again, off again with some getting the update very early while others, very late.
No matter though, folks in the Android Central forums are now reporting the update appears to of have been potentially sorted out and an influx of those unable to previously update to ICS are now getting the update notification on their devices. Have you got it yet? If so, let us know in the Android Central forums.