If you can't wait for Acer's tardy Android 4.0 update for its Iconia A100 and A500 Tabs, this might be of interest: leaked builds of Ice Cream Sandwich for both tablets have been posted over at xda-developers. They appear to be pretty stable with no major issues to report, though you will lose root access if you go through with the update. The builds also appear to feature fairly minimal skinning, which could be a sign that they are very early (the update isn't due for a couple of months, after all) — on the other hand, Acer has never been the most egregious offender when it comes to overzealous Android modifications. For more detailed impressions on the ins and outs of these builds, you can hit up the source links below.
Acer Iconia Tab A100 and A500 Android 4.0 builds leaked
Acer Iconia Tab A100 and A500 Android 4.0 builds leaked/
Leaked builds of the Android 4.0 update for Acer's Iconia A100 and A500 tablets have shown up on xda-developers.