Internet

[zachary1g]

You are expected to have problems connecting this day to web sites participating in IPv6 day. PMTUD is likely the cause.

Danger! IPv6 sorta works - however, large packets appear to fail, giving the appearance of a broken website. If a publisher publishes to IPv6, you will believe their web site to be broken. Ask your ISP about MTU issues; possibly with your tunnel.

[JKnott]

I have been using IPv6 for about a year and never had that problem.  It just works.  Also, IPv6 has a minimum MTU of 1280 bytes.