Is there any IPv6 application in Vista?
There is at least one Vista application that is only IPv6 - Windows Meeting Space (formerly Windows Collaboration). This has some consumer usage scenarios. The P2P platform that is in Vista is also v6-only, so as applications and games build on this platform, you'll see more usage of v6. There are transition technologies in Vista to allow v6 to work over v4 networks, so the world doesn't need to convert overnight.
The transition technologies in Vista allow IPv6 only applications to work across an IPv4 network. The Windows Meeting Space application should open the right ports for you firewall to make it work appropriately.