Hi Peter,
When you say that it doesn't work, do you mean that no "show" commands are allowed, or actually some of them work?
What commands did you test with? If any command works.. what are the working and non-working ones?
Did you configure authorization in orde to return a privilege level through the shell profile that is suitable for the show commands that you're testing?
What errors do you get on the ACS and/or on the switch?
I hope this helps!
Regards,
Federico