As shown below, they have major issues with MTU size on their IPv6 network. This is a major inconvenience and affects IPv6 users regardless of whether the site they are visiting is IPv6 enabled or not. In addition, it affects other Automattic sites hosted on Edgewall such as Gravatar and Akismet.
Ping6 works ok:
jmccrohan@lambda:~$ ping6 s0.wp.com
PING s0.wp.com(2606:2800:234:1922:15a7:17bf:bb7:f09) 56 data bytes
64 bytes from 2606:2800:234:1922:15a7:17bf:bb7:f09: icmp_seq=1 ttl=55 time=34.9 ms
64 bytes from 2606:2800:234:1922:15a7:17bf:bb7:f09: icmp_seq=2 ttl=55 time=21.6 ms
64 bytes from 2606:2800:234:1922:15a7:17bf:bb7:f09: icmp_seq=3 ttl=55 time=25.9 ms
64 bytes from 2606:2800:234:1922:15a7:17bf:bb7:f09: icmp_seq=4 ttl=55 time=21.7 ms
--- s0.wp.com ping statistics ---
4 packets transmitted, 4 received, 0% packet loss, time 3004ms
rtt min/avg/max/mdev = 21.600/26.050/34.968/5.438 ms
Wget over IPv6 fails:
jmccrohan@lambda:~$ wget -6 http://s0.wp.com/wp-content/js/devicepx-jetpack.js
--2012-11-12 01:05:08-- http://s0.wp.com/wp-content/js/devicepx-jetpack.js
Resolving s0.wp.com (s0.wp.com)... 2606:2800:234:1922:15a7:17bf:bb7:f09
Connecting to s0.wp.com (s0.wp.com)|2606:2800:234:1922:15a7:17bf:bb7:f09|:80... connected.
HTTP request sent, awaiting response...
There is, however, a httpd listening on tcp6/80:
jmccrohan@lambda:~$ telnet s0.wp.com 80
Connected to cs82.wac.edgecastcdn.net.
Escape character is '^]'.
GET /index.html HTTP/1.1
This leads me to believe there is a MTU issue somewhere. Thankfully I'm not the only one who is experiencing this. It has been discussed here and here too. If you are having issues, please get in touch via the comments below. I'd like to compare traceroutes.
EDIT: Edgecast have gotten back to me and are investigating the issue.
EDIT 2: Edgecast have followed up via email to confirm that they have fixed the issue. Thanks Edgecast.