I get continuous reboot after 15.0 upgrade

I was just tring to upgrade from 14.3-RELEASE-p6 to 15.0-RELEASE, but I
am just getting continuous reboots now.  The system is an amd64 based
system running with zfs on root.  I first upgraded to 14.3-RELEASE-p7 as
directed, and then did the upgrade to 15.0-RELEASE.  I didn't see any
errors and everything seemed fine until I rebooted.  I don't see any
unusual messages in the startup, but then it reboots after saying that
it is starting local daemons.  Since I have zfs on root, I was able to
boot from a 14.3-RELEASE-p7 boot environment, but I can't run 15.0.

Does anybody have any suggestions on how to debug this since I don't see
anything useful in the log files?
-- 
Carl Johnson		carlj@peak.org