When booting from the installer CD you will get errors like uid 0 on /: file system full clogging up the screen right after the disk setup. Press ctrl+Z to get to the shell, then
mv /tmp/* /mnt/tmp rm -r /tmp ln -s /mnt/tmp /tmp fg
This has to be done after the disk setup so the filesystems are already created and mounted.
and installation will continue. Choose http as install source and enter the server name mirror1.us.bitrig.org. It complained about the SHA256 sums of the downloaded files not matching what is expected, but it worked anyway.
EDIT: Snapshots seem to be gone, can’t find any currently. Dunno what’s up with that…