I don't really have any valuable input to help you along on this. I found that most people in a position of power usually never listen to those who are actually doing the work. I've discovered that most of the advice I gave were never actually taken to heart. :-\

What I can offer you is a little nugget. I would advise against the simple statement of, "Microsoft sucks." In a pinch it makes you look unprofessional. Pointy haired bosses like long, but simple explanations (counterintuitive). You mention that you get more support from PM than you do from MS. You could quantify that by saying something like, "Microsoft support will cost us money whereas the free support offered by Perl Monks is on par, if not better, than any paid support from Microsoft." Or something along those lines. Bosses like to lower their perceived costs and get the most bang for their buck.

Be sure that you present true facts though. You mention UNIX, so he'll certainly know his stuff, if not verify your information.