One other HUGE factor... Google sees
https://site.com as a different site from
http://site.com, so you're going to see at least a short term drop in Google rank.
The other issue, if you trade traffic with other sites that track incoming via referring URL, they'll need to update their tracking script to look for the https instead of the http. Some scripts can't do that.
I found out the above when I switched to https about a year ago. I had to switch back to http after about a month due to the huge drop in trade traffic. I had fallen out of the list on far far too many of the sites I've traded with for 10+ years.