I am a happy single stacked IPv6 user for a week now, and, as you might have imagined, some things do not work.
So, what I am exactly referring too?
As experienced before by Jari Arkko (http://tools.ietf.org/html/draft-arkko-ipv6-only-experience-00) IMs do not work. This, at that specific point was my biggest discomfort, as, to talk to anyone online, I had to revert to e-mails, which was a pain!
I found a solution today, which, I am still wondering why did it take for me so long to figure it out! Meebo!!!! Works flawless!
Of course, Skype is still out of game, but, at least we have a start!