We host over 2500 web sites, using 3 IP addresses. We have been using name-based virtualhosting for over 2 years now. Win2k, etc other servers out there also. Yes, I am. They ARE vendor specific.
Sometime policies have to be firm.
I think it is erroneous to hold policies to vendor-specific limitations. I mean no disrespect but that is not current possible in IIS 4 or IIS 5.o. Ah, but that argument doesn't hold much water. I have several that do this with great results. I hope that helps.