Just fyi, the only thing I could get to work in my situation (auto-install .NET 2.0 assemblies via an ActiveX control on a web page) was to write a little exe myself that calls into the System.EnterpriseServices.Internal.Publish object methods to install
into the GAC and register it for interop. I could have used regasm to do the COM portion, but since some people do not have the 2.0 runtime in their path (and I didn't want to hard code it in the .inf file), I just did it through the exe.
If anybody wants details, I'd be happy to post them. It took me a good 3 hours to get everything working as it should, and I see no reason for anyone to go through the same pains I did!