I for one think the more incompatible V4 and V6 are the better! There are only two things that ever made any sense: 1) try as hard as possible to be fully inter-operable with each other, or 2) full clean break. Clearly, there was never a 100% consensus on the goal. As is now, I see it as a chance to start over with so many silly things (ie, 12 layers of NAT for everything in the cloud). When you look at all the gripping about problems, it's so much of a better pitch to think of it as this new global network to play with that opens more doors instead of some never-going-to-happen retrofit from hell.