The main change you will see going from 6.6 to 6.7 is the new licensing model , please read the tech note and release notes
To convert your licenses to 6.7 all you need to do is go to the HPE portal or ASP.arubanetworks.com (if you already migrated your account) and convert your licenses
You have 6 months to do the license conversion after you perform the upgrade.
I have a few customers running 6.7.4 with no issues
Thank you
Victor Fabian
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