After a long and painful upgrade (the last one or now seemingly two firmware updates available kept failing over air, Kies kept throwing up stumbling blocks on my desktop PC, and now I finally managed to upgrade through Kies on my Win 8 laptop, though it required two error messages, one Kies restart and one phone reconnect), my Danish Galaxy S2 (NEE Nordic code) is now running 4.1.2.
I was somewhat startled after the reboot by the very different looking design of login screen and notification bar, as well as having to go through a few information screens (initially I thought my phone had actually been reset). I don't remember anything that drastic when my Transformer TF300 tablet was upgraded to Jelly Bean.
Fortunately everything - including Apex Launcher - appears to be where it was before, aside from widgets having to be readded to the homescreens. I was also notified of the available upgrade to Google Now, which is up and running (even if most of the information cards available are as useless for me on my phone as they are on my tablet, the majority of the time).