If you do not want to wait until April to receive the official Android 4.0 update for Acer Iconia Tab A100 and A500, now you can try the leaked Android 4.0 ROM for two devices. Both of two ROMs work quite well, with no error significant will occur even though this is not the final build from Acer. ROM interface is quite similar to the original ROM, only a small change in color of the icon. You can download and reference how to update below. Be careful to copy important data before proceeding slightly.
How to up ROM:
1. Rename the downloaded file to update.zip
2. Copy it back the root of memory card
3. Turn device off, then press the button to increase volume. Hand still hold up volume button while you press the power button. Wait until the device reboots.
4. And now you had Android 4.0 on your device.