No none at all just make sure you read the notes. I seem to remember that sometimes there is a note saying firmware upgrade needed. This is a major PITA don't bother.
I checked compatibility and S&S says that the TTL function is compatible with my EM5... any reason not to trust this?
Go with manual you'll have the hang of it in a couple of dives. Study strobe positioning then the power is easy to sort. I practiced at home in a dark bedroom and in varying light levels, if I couldn't go diving it gave me time to practice my skills