I've spoken with another developer or three that tell me that, although ActiveX controls remain supported, security policies have changed in some meaningful way

I've spoken with another developer or three that tell me that, although ActiveX controls remain supported, security policies have changed in some meaningful ways between versions of IE. The result is that your controls that were working fine in IE 6 stop working in later versions of IE. I have not personally confirmed this (and god send that I will never have to).