Overall, flank speed has been awesome, with the major issue being not everyone is migrated on email yet, and the migrations seemed to grind to a halt a few months ago.
FlankSpeed has the potential to be awesome if you have your own machine and/or you're big into the 365 world. But for a huge portion of the fleet who shares computers, it has added additional overhead of basic admin, and that admin is expected to be done by the end user. One big issue is if you convert on one computer, you still have to reconfigure Outlook on every other computer you log into in order to get your crypto to work (ie, be able to send emails).
There's even further confusion with the email identities. Everyone is told they now have a new us.navy.mil email, but they're old email is actually still how the system identifies you, which again, causes confusion for the end user. I'm not really sure what was accomplished by changing the domains other than some DoD alignment, although I did get rid of the stupid "1" at the end of my name. If I was "1", then did I really need a "1"?
I'm also amused that you don't always need CAC now, but I have no idea what my NMCI password is. I don't ever recall entering one. Maybe when I SpankFled, but again, it wasn't clear I needed to know that.