For those with an interest in "the technical stuff", and those who might not realise just how complicated some problems are, I came across some interesting reading that is IPv6 related.
First, a blog post from ThousandEyes (a network/system performance monitoring tool) which is clearly pushing how their tool can be used to investigate the problem
http://blog.thousandeyes.com/troubleshooting-path-mtu-tcp-mss-problems/Part way down it starts to cover PMTUD failure in IPv6. PMTUD is Path MTU Discovery - a process whereby two communicating nodes discover the size of the largest packet that can be passed between them (basically the "weakest link" in the chain of connections. This can fail, and when it does it causes problems.
In that blog post, there are links to
http://www.nlnetlabs.nl/downloads/publications/pmtu-black-holes-msc-thesis.pdf which covers it at thesis level
, and
https://labs.ripe.net/Members/gih/counting-ipv6-in-the-dns which attempts to put numbers on the proportion of "IPv6 capable" DNS infrastructure and how much of it suffers from the problem - it paints a "mixed" picture.
Of course, to anyone not interested in the technicalities, they could also help if you have insomnia