I attempted to upgrade my Digital Ocean VPS from FreeBSD 10 to 12 and I managed to wreck it. Not just a little either, it took me hours just to get to a state where I could access my files on a console again using a recovery disc. I ended up having to give up on salvaging the installation, but I've learned what I did wrong and successfully spun up another VPS and upgrade from 11 -> 12 without breaking it.
Took me a little time to get my configuration back to a state where I could serve my blog again, but I'm up, and upgraded all around (Rails, Ruby, Nginx, etc). I plan to do a visual refresh soon, I don't know that I'll really do anything different but I want to at least serve the existing images in a way that will look nice on high res displays.
I've got a couple more websites that existed on that VPS to restore, but I'm thinking it shouldn't take long at this point and then I may start porting over some of the websites I had hosted on Linode.