It has been a log time since I last post on this mailing list, but I never missed to use and enjoy this tool.
I just found on the freebsd-jail mailing list that there is a bit of excitement about Jail management tools out there... until now, besides the challenges the latest FreeBSD version bring to ezjail (the new stock configuration file format), I'm firmly trust ezjail for managing and updating base code and packages for about 70 jails spread among 10 hosts running FreeBSD 9.3.
Just a stupid point I just noted: the version shown by the 3.4.1 release is still the 3.3.
# pkg query %n-%v ezjail
Usage: ezjail-admin [...]
Unfortunately I'm still too busy at work to give back as I wish. The only thing you surely can count me on: I'll keep up advocating your solution among all sysadmins I meet.