I only have to worry about the change once a year as far as major things go. Which is what I was alluding to.
Comfort levels? I usually wear a hoodie with 1-2 layers down to 32, then my coat for everything below that with layers added the colder it gets.
I live in Michigan so the transition seasons are a crap-shoot on what you'll need to wear that day anyways so I have to keep clothes in my car either way temperature is measured.
The speed thing would be difficult for me as I'm into car culture so with that I'm far too used to MP/H.
Speed limits and driving would be easy as I have a VW with nice clear gauging for both speeds and my info center I think can be switched over anyways.
Horsepower/torque numbers are also what the fuck. That might be a British thing though. What is the most common measurement for that outside the US?
The temp thing I still don't think I could ever change. Not like I would do it in a way that would affect people.
I already use celcius as much I can outside of temp.