i upgraded from 7.2.2 to 7.3 and here are my lessons learned (about 150 devices)
the upgrade was expected to be .50 - 1 hour + according to the installer, it actually took about 5-10 minutes
i ran into a weird scenario poller wise. 7.2.2 hit the devices from the poller NCM was installed on, not the case with 7.3. with the upgrade if you are running an additional NPM poller (which i was) you will need to install an NCM additional poller also. since i had not done this and i restrict TTY access i had to migrate everything from the 2nd poller in NPM to the first so that i could run the script to update the TTY ACL to allow the 2nd poller access. then i had to migrate these same devices back to the additional poller. once i did this it worked like a champ!