Hi Chris,
I might be wrong but AIUI, the new functionality is that you can enable http and/or https rather than one or the other as it was in 7.5?
We went with https from day 1 in 7.5 as I knew CEM was a priority for us and that only works over https. Since we needed https for that we went https for everything. You need a certificate but if all your machines are in an Active Directory you can use one from there if you're too mean to get a "proper one". I guess there's a bit of an overhead with https but, like I said, we didn't have a choice.
Under Settings -> SMA there's a Symantec Agent Communication profiles section which you might want to look at - might shed light on how to switch over? Not sure if there's a way of forcing it.
Regards
Martin