https://bugzilla.gnome.org/show_bug.cgi?id=556915 and https://bugs.launchpad.net/ubuntu/+source/network-manager/+bug/307598 are the ones to watch if you have an IPv6-only network and Linux nodes. The older versions of the network manager assumed that the network that did not have IPv4 is "broken".
When I have a chance to test how this behaves in 10.10, I will update this entry.
10.10 has a much better knowledge of IPv6. So far I am pretty happy. To be tested is an IPv6-only network, but for that I need to install NAT64+DNS64, which I am not sure when I am able to do.