Yeah, I didn't want to go the sharing route for every reason you mentioned. It's pretty bad.

So you think it might be as easy as simply pointing two iTunes installations at the same set of files? I guess that makes sense. If I updated the library from one iTunes instance, I assume it would update the library (it's an XML file, isn't it?) and the other iTunes instance would see it the next time it was started up. Am I thinking correctly here?

Thanks for the tips. I'll be trying this on Friday when I have some time.