Not sure how or why, but was able to boot after n'th time.
I updated /etc/default/grub to remove "quiet" and "splash" and then ran sudo update-grub and reboot. Boot hangs on:
Starting Network Manager Script Dispatcher Service...
There are some google results, but nothing I saw specific to Ubuntu and relevant.
see also:
Ubuntu 16.10 freezes at startup
Upgrade from Ubuntu 14.04 to Ubuntu 14.10 Network-Manager fails to start on boot
