I won't be the first to opine this, but the worst thing about v6 is the lingo.
I (eventually) got the heads of my dependents, both at work and closer to home, around the concept of an IPv4 address. Four integers with dots in between. Sort of like a phone number, in that the format was consistent.
IPv6? 8 numbers in hex notation (with which we're all super comfortable, yeah), colon-delimited, which if they happen to be zero can be omitted, and if a number of them adjacent to each other are zero the colons can also be omitted just to make it extra opaque.
Do people really not get this? It's too much. Joe sixpack does not want to speak hexadecimal, nor to make sense of which address components are elided or why. If the address is reliably eight integers, with colons or periods or fucking Euro symbols delimiting them, that he can grok (possibly with help). IPv6 address notation is design by engineers, for engineers; granny need not apply.