There are more problems with wireless and CM7 besides hidden bssids. Having tested multiple accesspoints with different configs my conclusions are:
-unencrypted APs always work
-WPA2-PSK works sometimes:
-the CM7 accesspoint on my Desire Z always works
-a FON AP rarely works (managed to connect once)
-WPA2-EAP rarely works (only managed to connect a couple of times, mostly after reboots)
I'd really like to get CM7 to run, but this is a showstopper for me. "Good thing" is that apparently this bug is also randomly present on other devices running CM7, I trust the cause will we found and repaired soon.