Fred,
The widely-deployed implementations I am aware of are in Windows XP and Vista, cisco IOS, *BSD/Kame, and an older version of the Linux/USAGI kernel. There are probably others as well.
IPv6 is also found in Windows XP and Vista, cisco IOS, and Linux. Do we count this as accepted and no need to push for more acceptance because IPv6 is available in more than 80% of all computers (assuming that not all of the 90% that are running Windows are running XP or Vista)? How is this in actual usage? which networks are carrying traffic ? what companies have deployed it?
being available is not the same as widely deployed.