Yeah, until you run a website where you're getting 1000s of hits from some IPs, and you can't tell if that's a small business, a hacker at home, or a large enterprise - you will treat the three differently if you're getting that kind of traffic from each. Also, newer IM programs have to use UPnP to try to get a port open (which many corporate firewalls still don't support, even with restrictions).

I've just recently deployeed Apple Airport Extremes that support IPv6 on my network, and we are somewhat cutting edge, so I may turn on IPv6 on those soon.