It's been a pretty painless process on PC so far, aside from some save-game overwriting BS. I do get wierd framerate slowdowns from time to time, Don't know why, it always passes in a few seconds. I tried updating my nvidia driver from 158.x to the latest (160.x) and then the game crashed every hour or so, so i rolled it back. slowdowns are annoying, but I can deal with them. I have the settings on Ultra, and if i really wanted to i could prolly just lower them and it would go away. but I don't want to!
I also had weird slow downs randomly (at least it seemed random), but after a while I realized it was when ever there was a large group of NPC's on screen. According to another forum member, you can hit the tilde key (the ~ key), and in the console enter "toggleEmotions".
This make absolutely no visual difference that I could see, but now I never get any slowdowns. The only annoying bit is that I must re-enter this command every time I start the game.