That is not the case, except for 5585-X, the Sec Plus license is required on BOTH units in an HA configuration.

Thanks for the link.  I see that the command is supported in transparent mode only but I think I found a way to make this work in routed mode (which is what I have mine in) on the ASA 5505: x-asa# show switch mac-address-tableLegend: Age - entry expi...

Did you ever find out why this is.  I am running asa821-k8.bin on a 5505 and I get the following:x-asa# show mac-address-table                           ^ERROR: % Invalid input detected at '^' marker.