Captive Portal doesn't work on 2.1 snapshots
Most recently tried on the 7 March snapshot, but I see from Bug 1700 in Redmine that it's been around for awhile, with the implication that this is a regression caused by the inclusion of the IPv6 support.
At least part of the problem, as reported in the bug (and somewhat confirmed by my own observation), seems to be that the lighttpd instance used by the captive portal on TCP port 8000 only binds itself to localhost (127.0.0.1). The result is that the redirect to the captive portal hangs waiting for the login page. Another manifestation of this bug (I think) is that the "View Portal Page" link on the configuration screen for a captive portal instance also hangs.
With this in mind, if I comment out the server.bind line in /var/etc/lighty-guest-CaptivePortal.conf and restart that lighttpd instance, I can at least get the login screen on the client system. After a correct login, I do see the login on the captive portal status display on the Web UI, but I'm not able to get any traffic through the captive portal.
I know basically zero about pfSense's captive portal implementation or PHP, so I'm not sure how I can help with fixing this other than just bring up the issue again. Suggestions appreciated.