...In _one_ customer deployment We're deploying 1.7 million devices over 1200 mobile subnetworks in under 18 months. Each device needs to be capable of self addressing and migrating from subnetwork to subnetwork subject to the local RF conditions.
These devices need to be uniquely addressable from existing Unix hosts, as well as capable of being monitored from current Enterprise Network Element Managers.
We've further hypothesized that by 2012 as many as fifty of these networks will be in existence, each of which may need to have all their nodes addressable by multiple vendors.
There is your business case for IPV6.
Ironically, internally, in our company, and on all of our servers - we are 100% split stack. No desire whatsoever to run IPV6 pure environments. NAT does everything we need. Don't even run IPV6 on our IPSEC Remote Access VPN or 802.11 environment.