Back to installing Office Extensions. I have virtual servers setup by the header mechanism. I have virtual sites and separate ASP applications under most of the servers. They all run on standard port and a single IP address. It should upgrade, I haven't personally seen any issues with multiple virtual servers.
Testing is the key in a production environment.
I would be careful about running an upgrade on a lot of servers. The few of these fixes that also apply to NT4 will be available in the forthcoming SR1 release of Office. Sorry, I meant default port. Sorry, I don't know which one you are referring to. Previously it was mentioned that Port 80 was required for the Office Extensions.