By far the biggest headache with IPv6 is that they stop being easy for human's to read and comprehend
An experienced network engineer can look at the issued IPv4 ranges on a PC and work out why they may be having issues accessing the internet / network resources / VPN etc.
To do the same on IPv6 takes a lot more knowledge and understanding, if it's even possible at all
Therefore, pain in the arse to switch over.
Biting the hand that feeds IT
