Just for the record, IPv6 is definitely far from perfect…   There were things put in the specification that had no real world experience (some of which has since been deprecated), and some cases where tradeoffs were made that missed huge opportunities. 

However, neither the extra cruft nor the missed opportunities really got in the way of deployment – we are the present situation because we made a decision on the next IP protocol (IPv6) despite lacking the required "a straightforward transition plan from IPv4” – that was left as an exercise for the reader.  Absent a clear bridge from here to there, it shouldn’t be surprising that there was no serious deployment for more than a decade… 

After several years of non-solutions out of the IETF, the "very large" network operator community (who realized that they were indeed going to need IPv6 for their broadband and mobile deployments) waded in and came up with workable IPv6 transition solutions.  To this day, IPv6 remains essential to those with very large and growing networks, and less so for those with modest or no growth. 

FYI,

/John