Well that's good to know.
I'm on 4.2, I downgraded from 9.2 yesterday. I think formatting might be the solution since my 3ds had already downloaded the latest update and was constantly nagging me to install it. Although after downgrading it hasn't seemed to ask me to update anymore.
Anyway I'm going to format right now, I'll report my results asap.
Did you eshop downloads and saves even survive the downgrade process?