Don't be concerned about the number of "bars." Those are not a standard measure. They represent an arbitrary indication of the strength of the received signal only. The actual signal strength is controlled entirely by your router and not your tablet, and the tablet does not attenuate that. The signal received by the tablet from any unchanged AP that you were using is as strong as it was before the ICS update. The translation of the RSSI to the number of bars shown in the icon is all that changed with respect to that in ICS, and that is not a problem.
If you had taken benchmark measurements with the Speedtest app prior to the update and nothing else changed in your network, you would have seen equivalent performance between HC and ICS.
Now keep in mind that the wifi antennas on tablets are in places that are often obstructed by hands, etc., so just rotating a tablet 45 degrees can cause a significant change in the observed signal strength, so if you are having connectivity problems, that's useful to know. The a500 reception is not as good as that seen on a number of other tablets either, and that seems to be mainly due to differences in construction materials and antenna placement. The update to ICS did not change any of that though.
